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	$166.50	3.680%	$172.6272	$172.63	$172.65	$172.60
Purchase #2	$39.25	3.672%	$40.6913	$40.69	$40.70	$40.70
Purchase #3	$203.58	3.661%	$211.0331	$211.03	$211.05	$211.00
Purchase #4	$85.36	3.348%	$88.2179	$88.22	$88.20	$88.20
Purchase #5	$34.83	6.267%	$37.0128	$37.01	$37.00	$37.00
Purchase #6	$67.36	6.626%	$71.8233	$71.82	$71.80	$71.80
Purchase #7	$79.60	11.311%	$88.6036	$88.60	$88.60	$88.60
7 purchase totals =	$676.48		$710.0092	$710.00	$710.00	$709.90