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	$218.90	8.741%	$238.034	$238.03	$238.05	$238.00
Purchase #2	$31.77	11.200%	$35.3282	$35.33	$35.35	$35.30
Purchase #3	$104.97	13.107%	$118.7284	$118.73	$118.75	$118.70
Purchase #4	$90.95	6.550%	$96.9072	$96.91	$96.90	$96.90
Purchase #5	$234.33	9.651%	$256.9452	$256.95	$256.95	$256.90
Purchase #6	$139.62	9.283%	$152.5809	$152.58	$152.60	$152.60
Purchase #7	$63.72	13.674%	$72.4331	$72.43	$72.45	$72.40
7 purchase totals =	$884.26		$970.9570	$970.96	$971.05	$970.80