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	$83.77	4.824%	$87.8111	$87.81	$87.80	$87.80
Purchase #2	$241.60	9.591%	$264.7719	$264.77	$264.75	$264.80
Purchase #3	$49.69	10.642%	$54.978	$54.98	$55.00	$55.00
Purchase #4	$28.68	7.774%	$30.9096	$30.91	$30.90	$30.90
Purchase #5	$162.65	7.814%	$175.3595	$175.36	$175.35	$175.40
Purchase #6	$37.95	7.742%	$40.8881	$40.89	$40.90	$40.90
Purchase #7	$48.82	11.766%	$54.5642	$54.56	$54.55	$54.60
7 purchase totals =	$653.16		$709.2824	$709.28	$709.25	$709.40