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	$91.67	12.208%	$102.8611	$102.86	$102.85	$102.90
Purchase #2	$155.30	8.417%	$168.3716	$168.37	$168.35	$168.40
Purchase #3	$241.93	13.727%	$275.1397	$275.14	$275.15	$275.10
Purchase #4	$61.59	9.800%	$67.6258	$67.63	$67.65	$67.60
Purchase #5	$92.63	13.805%	$105.4176	$105.42	$105.40	$105.40
Purchase #6	$82.89	10.160%	$91.3116	$91.31	$91.30	$91.30
Purchase #7	$203.36	6.125%	$215.8158	$215.82	$215.80	$215.80
7 purchase totals =	$929.37		$1,026.5432	$1,026.55	$1,026.50	$1,026.50