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	$62.83	9.666%	$68.9031	$68.90	$68.90	$68.90
Purchase #2	$99.91	13.387%	$113.285	$113.29	$113.30	$113.30
Purchase #3	$101.48	11.513%	$113.1634	$113.16	$113.15	$113.20
Purchase #4	$53.98	10.590%	$59.6965	$59.70	$59.70	$59.70
Purchase #5	$115.86	6.460%	$123.3446	$123.34	$123.35	$123.30
Purchase #6	$128.97	5.718%	$136.3445	$136.34	$136.35	$136.30
Purchase #7	$71.53	6.768%	$76.3712	$76.37	$76.35	$76.40
7 purchase totals =	$634.56		$691.1083	$691.10	$691.10	$691.10