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	$17.62	9.628%	$19.3165	$19.32	$19.30	$19.30
Purchase #2	$153.92	5.185%	$161.9008	$161.90	$161.90	$161.90
Purchase #3	$159.61	5.512%	$168.4077	$168.41	$168.40	$168.40
Purchase #4	$209.27	3.399%	$216.3831	$216.38	$216.40	$216.40
Purchase #5	$224.67	13.693%	$255.4341	$255.43	$255.45	$255.40
Purchase #6	$39.94	10.593%	$44.1708	$44.17	$44.15	$44.20
Purchase #7	$78.80	4.566%	$82.398	$82.40	$82.40	$82.40
7 purchase totals =	$883.83		$948.0110	$948.01	$948.00	$948.00