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	$73.65	11.570%	$82.1713	$82.17	$82.15	$82.20
Purchase #2	$66.26	9.515%	$72.5646	$72.56	$72.55	$72.60
Purchase #3	$88.50	13.588%	$100.5254	$100.53	$100.55	$100.50
Purchase #4	$189.74	5.564%	$200.2971	$200.30	$200.30	$200.30
Purchase #5	$75.55	11.432%	$84.1869	$84.19	$84.20	$84.20
Purchase #6	$108.49	13.825%	$123.4887	$123.49	$123.50	$123.50
Purchase #7	$105.46	7.508%	$113.3779	$113.38	$113.40	$113.40
7 purchase totals =	$707.65		$776.6119	$776.62	$776.65	$776.70