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	$75.82	13.807%	$86.2885	$86.29	$86.30	$86.30
Purchase #2	$193.87	9.418%	$212.1287	$212.13	$212.15	$212.10
Purchase #3	$199.57	11.461%	$222.4427	$222.44	$222.45	$222.40
Purchase #4	$20.70	3.644%	$21.4543	$21.45	$21.45	$21.50
Purchase #5	$59.33	12.492%	$66.7415	$66.74	$66.75	$66.70
Purchase #6	$111.45	4.266%	$116.2045	$116.20	$116.20	$116.20
Purchase #7	$6.35	10.623%	$7.0246	$7.02	$7.00	$7.00
7 purchase totals =	$667.09		$732.2848	$732.27	$732.30	$732.20