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	$99.26	5.111%	$104.3332	$104.33	$104.35	$104.30
Purchase #2	$20.42	12.144%	$22.8998	$22.90	$22.90	$22.90
Purchase #3	$226.82	9.593%	$248.5788	$248.58	$248.60	$248.60
Purchase #4	$60.90	10.122%	$67.0643	$67.06	$67.05	$67.10
Purchase #5	$5.25	11.550%	$5.8564	$5.86	$5.85	$5.90
Purchase #6	$74.71	3.476%	$77.3069	$77.31	$77.30	$77.30
Purchase #7	$36.25	3.195%	$37.4082	$37.41	$37.40	$37.40
7 purchase totals =	$523.61		$563.4476	$563.45	$563.45	$563.50