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	$191.67	13.401%	$217.3557	$217.36	$217.35	$217.40
Purchase #2	$174.78	3.640%	$181.142	$181.14	$181.15	$181.10
Purchase #3	$201.45	3.827%	$209.1595	$209.16	$209.15	$209.20
Purchase #4	$215.91	10.488%	$238.5546	$238.55	$238.55	$238.60
Purchase #5	$66.94	10.392%	$73.8964	$73.90	$73.90	$73.90
Purchase #6	$170.31	10.802%	$188.7069	$188.71	$188.70	$188.70
Purchase #7	$111.41	4.528%	$116.4546	$116.45	$116.45	$116.50
7 purchase totals =	$1,132.47		$1,225.2697	$1,225.27	$1,225.25	$1,225.40