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	$118.99	5.129%	$125.093	$125.09	$125.10	$125.10
Purchase #2	$131.46	6.665%	$140.2218	$140.22	$140.20	$140.20
Purchase #3	$97.71	5.772%	$103.3498	$103.35	$103.35	$103.30
Purchase #4	$63.71	13.486%	$72.3019	$72.30	$72.30	$72.30
Purchase #5	$110.48	12.357%	$124.132	$124.13	$124.15	$124.10
Purchase #6	$77.66	7.640%	$83.5932	$83.59	$83.60	$83.60
Purchase #7	$42.88	13.118%	$48.505	$48.51	$48.50	$48.50
7 purchase totals =	$642.89		$697.1967	$697.19	$697.20	$697.10