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	$210.65	13.115%	$238.2767	$238.28	$238.30	$238.30
Purchase #2	$187.50	13.462%	$212.7413	$212.74	$212.75	$212.70
Purchase #3	$217.77	7.181%	$233.4081	$233.41	$233.40	$233.40
Purchase #4	$48.41	9.398%	$52.9596	$52.96	$52.95	$53.00
Purchase #5	$113.30	12.394%	$127.3424	$127.34	$127.35	$127.30
Purchase #6	$91.93	3.874%	$95.4914	$95.49	$95.50	$95.50
Purchase #7	$82.57	12.109%	$92.5684	$92.57	$92.55	$92.60
7 purchase totals =	$952.13		$1,052.7879	$1,052.79	$1,052.80	$1,052.80