Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$210.93	6.114%	$223.8263	$223.83	$223.85	$223.80
Purchase #2	$185.88	3.582%	$192.5382	$192.54	$192.55	$192.50
Purchase #3	$188.31	6.523%	$200.5935	$200.59	$200.60	$200.60
Purchase #4	$234.27	4.267%	$244.2663	$244.27	$244.25	$244.30
Purchase #5	$114.28	10.486%	$126.2634	$126.26	$126.25	$126.30
Purchase #6	$167.64	13.406%	$190.1138	$190.11	$190.10	$190.10
Purchase #7	$162.69	10.759%	$180.1938	$180.19	$180.20	$180.20
7 purchase totals =	$1,264.00		$1,357.7953	$1,357.79	$1,357.80	$1,357.80