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	$36.33	3.683%	$37.668	$37.67	$37.65	$37.70
Purchase #2	$80.85	3.505%	$83.6838	$83.68	$83.70	$83.70
Purchase #3	$165.60	6.652%	$176.6157	$176.62	$176.60	$176.60
Purchase #4	$168.98	12.604%	$190.2782	$190.28	$190.30	$190.30
Purchase #5	$200.33	6.704%	$213.7601	$213.76	$213.75	$213.80
Purchase #6	$55.54	10.551%	$61.4	$61.40	$61.40	$61.40
Purchase #7	$178.74	11.255%	$198.8572	$198.86	$198.85	$198.90
7 purchase totals =	$886.37		$962.2630	$962.27	$962.25	$962.40