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	$99.51	11.183%	$110.6382	$110.64	$110.65	$110.60
Purchase #2	$55.93	11.635%	$62.4375	$62.44	$62.45	$62.40
Purchase #3	$56.33	3.680%	$58.4029	$58.40	$58.40	$58.40
Purchase #4	$152.63	8.542%	$165.6677	$165.67	$165.65	$165.70
Purchase #5	$90.52	10.264%	$99.811	$99.81	$99.80	$99.80
Purchase #6	$195.48	9.232%	$213.5267	$213.53	$213.55	$213.50
Purchase #7	$82.47	4.627%	$86.2859	$86.29	$86.30	$86.30
7 purchase totals =	$732.87		$796.7699	$796.78	$796.80	$796.70