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	$114.81	8.588%	$124.6699	$124.67	$124.65	$124.70
Purchase #2	$139.38	6.583%	$148.5554	$148.56	$148.55	$148.60
Purchase #3	$213.69	7.554%	$229.8321	$229.83	$229.85	$229.80
Purchase #4	$165.30	5.320%	$174.094	$174.09	$174.10	$174.10
Purchase #5	$91.95	10.251%	$101.3758	$101.38	$101.40	$101.40
Purchase #6	$55.71	11.782%	$62.2738	$62.27	$62.25	$62.30
Purchase #7	$94.66	11.284%	$105.3414	$105.34	$105.35	$105.30
7 purchase totals =	$875.50		$946.1424	$946.14	$946.15	$946.20