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	$175.38	9.491%	$192.0253	$192.03	$192.05	$192.00
Purchase #2	$100.84	4.352%	$105.2286	$105.23	$105.25	$105.20
Purchase #3	$92.25	8.511%	$100.1014	$100.10	$100.10	$100.10
Purchase #4	$50.94	4.462%	$53.2129	$53.21	$53.20	$53.20
Purchase #5	$187.62	4.857%	$196.7327	$196.73	$196.75	$196.70
Purchase #6	$27.90	3.784%	$28.9557	$28.96	$28.95	$29.00
Purchase #7	$167.72	9.124%	$183.0228	$183.02	$183.00	$183.00
7 purchase totals =	$802.65		$859.2794	$859.28	$859.30	$859.20