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	$144.77	4.504%	$151.2904	$151.29	$151.30	$151.30
Purchase #2	$202.64	6.161%	$215.1247	$215.12	$215.10	$215.10
Purchase #3	$158.54	4.104%	$165.0465	$165.05	$165.05	$165.00
Purchase #4	$36.34	9.188%	$39.6789	$39.68	$39.70	$39.70
Purchase #5	$151.39	3.373%	$156.4964	$156.50	$156.50	$156.50
Purchase #6	$243.41	5.423%	$256.6101	$256.61	$256.60	$256.60
Purchase #7	$179.89	3.109%	$185.4828	$185.48	$185.50	$185.50
7 purchase totals =	$1,116.98		$1,169.7298	$1,169.73	$1,169.75	$1,169.70