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	$36.81	12.873%	$41.5486	$41.55	$41.55	$41.50
Purchase #2	$134.27	9.144%	$146.5476	$146.55	$146.55	$146.50
Purchase #3	$93.57	6.109%	$99.2862	$99.29	$99.30	$99.30
Purchase #4	$60.59	12.125%	$67.9365	$67.94	$67.95	$67.90
Purchase #5	$196.94	13.292%	$223.1173	$223.12	$223.10	$223.10
Purchase #6	$250.82	4.779%	$262.8067	$262.81	$262.80	$262.80
Purchase #7	$184.39	10.387%	$203.5426	$203.54	$203.55	$203.50
7 purchase totals =	$957.39		$1,044.7855	$1,044.80	$1,044.80	$1,044.60