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	$246.80	10.490%	$272.6893	$272.69	$272.70	$272.70
Purchase #2	$72.35	11.336%	$80.5516	$80.55	$80.55	$80.60
Purchase #3	$59.79	3.307%	$61.7673	$61.77	$61.75	$61.80
Purchase #4	$80.92	9.663%	$88.7393	$88.74	$88.75	$88.70
Purchase #5	$89.67	6.192%	$95.2224	$95.22	$95.20	$95.20
Purchase #6	$43.52	13.360%	$49.3343	$49.33	$49.35	$49.30
Purchase #7	$99.75	5.823%	$105.5584	$105.56	$105.55	$105.60
7 purchase totals =	$692.80		$753.8626	$753.86	$753.85	$753.90