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	$89.46	10.185%	$98.5715	$98.57	$98.55	$98.60
Purchase #2	$214.32	10.381%	$236.5686	$236.57	$236.55	$236.60
Purchase #3	$68.61	11.579%	$76.5544	$76.55	$76.55	$76.60
Purchase #4	$81.41	12.642%	$91.7019	$91.70	$91.70	$91.70
Purchase #5	$115.74	9.750%	$127.0247	$127.02	$127.00	$127.00
Purchase #6	$159.64	12.435%	$179.4912	$179.49	$179.50	$179.50
Purchase #7	$91.34	9.289%	$99.8246	$99.82	$99.80	$99.80
7 purchase totals =	$820.52		$909.7369	$909.72	$909.65	$909.80