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	$35.31	5.678%	$37.3149	$37.31	$37.30	$37.30
Purchase #2	$168.46	8.870%	$183.4024	$183.40	$183.40	$183.40
Purchase #3	$134.68	4.803%	$141.1487	$141.15	$141.15	$141.10
Purchase #4	$133.59	7.161%	$143.1564	$143.16	$143.15	$143.20
Purchase #5	$161.30	5.172%	$169.6424	$169.64	$169.65	$169.60
Purchase #6	$196.66	12.546%	$221.333	$221.33	$221.35	$221.30
Purchase #7	$188.35	5.399%	$198.519	$198.52	$198.50	$198.50
7 purchase totals =	$1,018.35		$1,094.5168	$1,094.51	$1,094.50	$1,094.40