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	$192.30	12.523%	$216.3817	$216.38	$216.40	$216.40
Purchase #2	$20.29	6.272%	$21.5626	$21.56	$21.55	$21.60
Purchase #3	$59.41	3.639%	$61.5719	$61.57	$61.55	$61.60
Purchase #4	$15.46	8.737%	$16.8107	$16.81	$16.80	$16.80
Purchase #5	$91.32	12.683%	$102.9021	$102.90	$102.90	$102.90
Purchase #6	$35.92	11.708%	$40.1255	$40.13	$40.15	$40.10
Purchase #7	$93.69	9.278%	$102.3826	$102.38	$102.40	$102.40
7 purchase totals =	$508.39		$561.7371	$561.73	$561.75	$561.80