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	$171.67	13.782%	$195.3296	$195.33	$195.35	$195.30
Purchase #2	$112.55	13.834%	$128.1202	$128.12	$128.10	$128.10
Purchase #3	$111.95	7.391%	$120.2242	$120.22	$120.20	$120.20
Purchase #4	$65.68	9.723%	$72.0661	$72.07	$72.05	$72.10
Purchase #5	$244.95	12.859%	$276.4481	$276.45	$276.45	$276.40
Purchase #6	$51.29	5.724%	$54.2258	$54.23	$54.25	$54.20
Purchase #7	$81.89	4.730%	$85.7634	$85.76	$85.75	$85.80
7 purchase totals =	$839.98		$932.1774	$932.18	$932.15	$932.10