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	$110.50	4.212%	$115.1543	$115.15	$115.15	$115.20
Purchase #2	$99.55	6.432%	$105.9531	$105.95	$105.95	$106.00
Purchase #3	$137.72	10.749%	$152.5235	$152.52	$152.50	$152.50
Purchase #4	$217.78	9.130%	$237.6633	$237.66	$237.65	$237.70
Purchase #5	$103.45	3.129%	$106.687	$106.69	$106.70	$106.70
Purchase #6	$245.32	12.302%	$275.4993	$275.50	$275.50	$275.50
Purchase #7	$139.86	6.265%	$148.6222	$148.62	$148.60	$148.60
7 purchase totals =	$1,054.18		$1,142.1027	$1,142.09	$1,142.05	$1,142.20