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	$31.82	4.610%	$33.2869	$33.29	$33.30	$33.30
Purchase #2	$61.68	4.601%	$64.5179	$64.52	$64.50	$64.50
Purchase #3	$96.40	13.765%	$109.6695	$109.67	$109.65	$109.70
Purchase #4	$77.80	9.566%	$85.2423	$85.24	$85.25	$85.20
Purchase #5	$92.47	5.300%	$97.3709	$97.37	$97.35	$97.40
Purchase #6	$53.27	5.749%	$56.3325	$56.33	$56.35	$56.30
Purchase #7	$131.81	11.122%	$146.4699	$146.47	$146.45	$146.50
7 purchase totals =	$545.25		$592.8899	$592.89	$592.85	$592.90