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	$235.38	6.516%	$250.7174	$250.72	$250.70	$250.70
Purchase #2	$57.93	12.361%	$65.0907	$65.09	$65.10	$65.10
Purchase #3	$212.72	5.199%	$223.7793	$223.78	$223.80	$223.80
Purchase #4	$72.38	4.470%	$75.6154	$75.62	$75.60	$75.60
Purchase #5	$152.38	8.759%	$165.727	$165.73	$165.75	$165.70
Purchase #6	$104.63	7.525%	$112.5034	$112.50	$112.50	$112.50
Purchase #7	$174.52	10.626%	$193.0645	$193.06	$193.05	$193.10
7 purchase totals =	$1,009.94		$1,086.4977	$1,086.50	$1,086.50	$1,086.50