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	$52.92	11.531%	$59.0222	$59.02	$59.00	$59.00
Purchase #2	$64.75	10.570%	$71.5941	$71.59	$71.60	$71.60
Purchase #3	$42.82	6.139%	$45.4487	$45.45	$45.45	$45.40
Purchase #4	$7.63	8.644%	$8.2895	$8.29	$8.30	$8.30
Purchase #5	$94.45	11.461%	$105.2749	$105.27	$105.25	$105.30
Purchase #6	$8.27	12.370%	$9.293	$9.29	$9.30	$9.30
Purchase #7	$72.59	9.858%	$79.7459	$79.75	$79.75	$79.70
7 purchase totals =	$343.43		$378.6683	$378.66	$378.65	$378.60