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	$110.51	11.653%	$123.3877	$123.39	$123.40	$123.40
Purchase #2	$231.25	6.283%	$245.7794	$245.78	$245.80	$245.80
Purchase #3	$154.73	10.556%	$171.0633	$171.06	$171.05	$171.10
Purchase #4	$240.29	5.641%	$253.8448	$253.84	$253.85	$253.80
Purchase #5	$95.60	10.114%	$105.269	$105.27	$105.25	$105.30
Purchase #6	$107.32	3.755%	$111.3499	$111.35	$111.35	$111.30
Purchase #7	$172.62	6.743%	$184.2598	$184.26	$184.25	$184.30
7 purchase totals =	$1,112.32		$1,194.9539	$1,194.95	$1,194.95	$1,195.00