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	$78.64	13.254%	$89.0629	$89.06	$89.05	$89.10
Purchase #2	$131.52	13.102%	$148.7518	$148.75	$148.75	$148.80
Purchase #3	$95.78	9.359%	$104.7441	$104.74	$104.75	$104.70
Purchase #4	$240.71	5.457%	$253.8455	$253.85	$253.85	$253.80
Purchase #5	$125.47	3.617%	$130.0082	$130.01	$130.00	$130.00
Purchase #6	$174.37	13.871%	$198.5569	$198.56	$198.55	$198.60
Purchase #7	$94.70	5.463%	$99.8735	$99.87	$99.85	$99.90
7 purchase totals =	$941.19		$1,024.8429	$1,024.84	$1,024.80	$1,024.90