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	$58.79	5.767%	$62.1804	$62.18	$62.20	$62.20
Purchase #2	$250.96	13.587%	$285.0579	$285.06	$285.05	$285.10
Purchase #3	$124.74	9.619%	$136.7387	$136.74	$136.75	$136.70
Purchase #4	$111.66	5.805%	$118.1419	$118.14	$118.15	$118.10
Purchase #5	$158.49	6.336%	$168.5319	$168.53	$168.55	$168.50
Purchase #6	$78.50	13.614%	$89.187	$89.19	$89.20	$89.20
Purchase #7	$149.52	6.165%	$158.7379	$158.74	$158.75	$158.70
7 purchase totals =	$932.66		$1,018.5757	$1,018.58	$1,018.65	$1,018.50