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	$87.90	4.129%	$91.5294	$91.53	$91.55	$91.50
Purchase #2	$93.98	12.466%	$105.6955	$105.70	$105.70	$105.70
Purchase #3	$226.51	7.517%	$243.5368	$243.54	$243.55	$243.50
Purchase #4	$167.80	13.467%	$190.3976	$190.40	$190.40	$190.40
Purchase #5	$169.37	9.362%	$185.2264	$185.23	$185.25	$185.20
Purchase #6	$109.43	8.839%	$119.1025	$119.10	$119.10	$119.10
Purchase #7	$117.53	12.157%	$131.8181	$131.82	$131.80	$131.80
7 purchase totals =	$972.52		$1,067.3063	$1,067.32	$1,067.35	$1,067.20