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	$155.96	10.275%	$171.9849	$171.98	$172.00	$172.00
Purchase #2	$149.25	13.315%	$169.1226	$169.12	$169.10	$169.10
Purchase #3	$161.64	6.751%	$172.5523	$172.55	$172.55	$172.60
Purchase #4	$85.67	4.353%	$89.3992	$89.40	$89.40	$89.40
Purchase #5	$110.77	5.315%	$116.6574	$116.66	$116.65	$116.70
Purchase #6	$84.53	9.570%	$92.6195	$92.62	$92.60	$92.60
Purchase #7	$170.70	6.749%	$182.2205	$182.22	$182.20	$182.20
7 purchase totals =	$918.52		$994.5564	$994.55	$994.50	$994.60