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	$165.30	3.220%	$170.6227	$170.62	$170.60	$170.60
Purchase #2	$16.72	10.790%	$18.5241	$18.52	$18.50	$18.50
Purchase #3	$57.31	3.125%	$59.1009	$59.10	$59.10	$59.10
Purchase #4	$64.73	10.186%	$71.3234	$71.32	$71.30	$71.30
Purchase #5	$50.50	6.205%	$53.6335	$53.63	$53.65	$53.60
Purchase #6	$162.73	5.688%	$171.9861	$171.99	$172.00	$172.00
Purchase #7	$179.60	12.829%	$202.6409	$202.64	$202.65	$202.60
7 purchase totals =	$696.89		$747.8316	$747.82	$747.80	$747.70