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	$83.62	13.476%	$94.8886	$94.89	$94.90	$94.90
Purchase #2	$72.59	13.309%	$82.251	$82.25	$82.25	$82.30
Purchase #3	$109.32	3.252%	$112.8751	$112.88	$112.90	$112.90
Purchase #4	$180.33	7.226%	$193.3606	$193.36	$193.35	$193.40
Purchase #5	$79.57	9.272%	$86.9477	$86.95	$86.95	$86.90
Purchase #6	$94.42	12.155%	$105.8968	$105.90	$105.90	$105.90
Purchase #7	$26.34	6.502%	$28.0526	$28.05	$28.05	$28.10
7 purchase totals =	$646.19		$704.2724	$704.28	$704.30	$704.40