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	$58.74	4.195%	$61.2041	$61.20	$61.20	$61.20
Purchase #2	$59.49	13.871%	$67.7419	$67.74	$67.75	$67.70
Purchase #3	$82.45	4.212%	$85.9228	$85.92	$85.90	$85.90
Purchase #4	$122.55	9.766%	$134.5182	$134.52	$134.50	$134.50
Purchase #5	$216.97	11.734%	$242.4293	$242.43	$242.45	$242.40
Purchase #6	$143.34	11.315%	$159.5589	$159.56	$159.55	$159.60
Purchase #7	$154.31	12.839%	$174.1219	$174.12	$174.10	$174.10
7 purchase totals =	$837.85		$925.4971	$925.49	$925.45	$925.40