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	$85.64	6.678%	$91.359	$91.36	$91.35	$91.40
Purchase #2	$155.71	6.146%	$165.2799	$165.28	$165.30	$165.30
Purchase #3	$71.70	6.335%	$76.2422	$76.24	$76.25	$76.20
Purchase #4	$22.75	13.666%	$25.859	$25.86	$25.85	$25.90
Purchase #5	$159.63	7.213%	$171.1441	$171.14	$171.15	$171.10
Purchase #6	$49.65	9.524%	$54.3787	$54.38	$54.40	$54.40
Purchase #7	$142.31	10.303%	$156.9722	$156.97	$156.95	$157.00
7 purchase totals =	$687.39		$741.2351	$741.23	$741.25	$741.30