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	$121.59	4.488%	$127.047	$127.05	$127.05	$127.00
Purchase #2	$137.93	4.479%	$144.1079	$144.11	$144.10	$144.10
Purchase #3	$217.83	4.802%	$228.2902	$228.29	$228.30	$228.30
Purchase #4	$86.63	11.209%	$96.3404	$96.34	$96.35	$96.30
Purchase #5	$68.98	10.316%	$76.096	$76.10	$76.10	$76.10
Purchase #6	$18.90	8.776%	$20.5587	$20.56	$20.55	$20.60
Purchase #7	$17.53	12.553%	$19.7305	$19.73	$19.75	$19.70
7 purchase totals =	$669.39		$712.1707	$712.18	$712.20	$712.10