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	$148.62	3.602%	$153.9733	$153.97	$153.95	$154.00
Purchase #2	$80.50	12.146%	$90.2775	$90.28	$90.30	$90.30
Purchase #3	$248.29	10.797%	$275.0979	$275.10	$275.10	$275.10
Purchase #4	$207.89	9.846%	$228.3588	$228.36	$228.35	$228.40
Purchase #5	$56.54	3.409%	$58.4674	$58.47	$58.45	$58.50
Purchase #6	$42.87	3.286%	$44.2787	$44.28	$44.30	$44.30
Purchase #7	$152.95	8.374%	$165.758	$165.76	$165.75	$165.80
7 purchase totals =	$937.66		$1,016.2116	$1,016.22	$1,016.20	$1,016.40