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	$58.93	7.443%	$63.3162	$63.32	$63.30	$63.30
Purchase #2	$66.75	8.355%	$72.327	$72.33	$72.35	$72.30
Purchase #3	$26.67	8.245%	$28.8689	$28.87	$28.85	$28.90
Purchase #4	$236.80	11.521%	$264.0817	$264.08	$264.10	$264.10
Purchase #5	$109.62	6.404%	$116.6401	$116.64	$116.65	$116.60
Purchase #6	$62.37	5.131%	$65.5702	$65.57	$65.55	$65.60
Purchase #7	$166.48	3.748%	$172.7197	$172.72	$172.70	$172.70
7 purchase totals =	$727.62		$783.5238	$783.53	$783.50	$783.50