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	$194.50	12.698%	$219.1976	$219.20	$219.20	$219.20
Purchase #2	$232.80	12.713%	$262.3959	$262.40	$262.40	$262.40
Purchase #3	$165.57	3.605%	$171.5388	$171.54	$171.55	$171.50
Purchase #4	$104.35	11.698%	$116.5569	$116.56	$116.55	$116.60
Purchase #5	$35.72	11.344%	$39.7721	$39.77	$39.75	$39.80
Purchase #6	$105.91	4.822%	$111.017	$111.02	$111.00	$111.00
Purchase #7	$180.74	9.777%	$198.4109	$198.41	$198.40	$198.40
7 purchase totals =	$1,019.59		$1,118.8892	$1,118.90	$1,118.85	$1,118.90