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	$79.33	7.669%	$85.4138	$85.41	$85.40	$85.40
Purchase #2	$127.67	13.364%	$144.7318	$144.73	$144.75	$144.70
Purchase #3	$33.70	5.447%	$35.5356	$35.54	$35.55	$35.50
Purchase #4	$169.59	12.602%	$190.9617	$190.96	$190.95	$191.00
Purchase #5	$94.69	12.522%	$106.5471	$106.55	$106.55	$106.50
Purchase #6	$58.80	4.421%	$61.3995	$61.40	$61.40	$61.40
Purchase #7	$113.89	3.425%	$117.7907	$117.79	$117.80	$117.80
7 purchase totals =	$677.67		$742.3802	$742.38	$742.40	$742.30