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	$218.28	4.727%	$228.5981	$228.60	$228.60	$228.60
Purchase #2	$171.55	9.436%	$187.7375	$187.74	$187.75	$187.70
Purchase #3	$150.78	9.679%	$165.374	$165.37	$165.35	$165.40
Purchase #4	$95.58	6.560%	$101.85	$101.85	$101.85	$101.90
Purchase #5	$32.27	9.294%	$35.2692	$35.27	$35.25	$35.30
Purchase #6	$71.71	10.394%	$79.1635	$79.16	$79.15	$79.20
Purchase #7	$65.57	10.254%	$72.2935	$72.29	$72.30	$72.30
7 purchase totals =	$805.74		$870.2858	$870.28	$870.25	$870.40