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	$116.81	11.673%	$130.4452	$130.45	$130.45	$130.40
Purchase #2	$157.64	7.444%	$169.3747	$169.37	$169.35	$169.40
Purchase #3	$24.70	13.823%	$28.1143	$28.11	$28.10	$28.10
Purchase #4	$19.51	8.131%	$21.0964	$21.10	$21.10	$21.10
Purchase #5	$59.98	12.765%	$67.6364	$67.64	$67.65	$67.60
Purchase #6	$70.93	11.325%	$78.9628	$78.96	$78.95	$79.00
Purchase #7	$89.30	9.835%	$98.0827	$98.08	$98.10	$98.10
7 purchase totals =	$538.87		$593.7125	$593.71	$593.70	$593.70