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	$83.89	8.677%	$91.1691	$91.17	$91.15	$91.20
Purchase #2	$26.61	8.183%	$28.7875	$28.79	$28.80	$28.80
Purchase #3	$123.78	6.481%	$131.8022	$131.80	$131.80	$131.80
Purchase #4	$132.52	13.546%	$150.4712	$150.47	$150.45	$150.50
Purchase #5	$84.54	8.613%	$91.8214	$91.82	$91.80	$91.80
Purchase #6	$25.74	7.743%	$27.733	$27.73	$27.75	$27.70
Purchase #7	$248.75	10.744%	$275.4757	$275.48	$275.50	$275.50
7 purchase totals =	$725.83		$797.2601	$797.26	$797.25	$797.30