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	$229.80	7.401%	$246.8075	$246.81	$246.80	$246.80
Purchase #2	$99.31	9.719%	$108.9619	$108.96	$108.95	$109.00
Purchase #3	$83.84	7.735%	$90.325	$90.33	$90.35	$90.30
Purchase #4	$175.65	9.263%	$191.9205	$191.92	$191.90	$191.90
Purchase #5	$39.49	3.168%	$40.741	$40.74	$40.75	$40.70
Purchase #6	$67.56	7.700%	$72.7621	$72.76	$72.75	$72.80
Purchase #7	$245.68	13.469%	$278.7706	$278.77	$278.75	$278.80
7 purchase totals =	$941.33		$1,030.2886	$1,030.29	$1,030.25	$1,030.30