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	$57.58	6.412%	$61.272	$61.27	$61.25	$61.30
Purchase #2	$167.56	4.184%	$174.5707	$174.57	$174.55	$174.60
Purchase #3	$114.36	7.356%	$122.7723	$122.77	$122.75	$122.80
Purchase #4	$50.62	3.695%	$52.4904	$52.49	$52.50	$52.50
Purchase #5	$94.57	5.601%	$99.8669	$99.87	$99.85	$99.90
Purchase #6	$171.71	4.528%	$179.485	$179.49	$179.50	$179.50
Purchase #7	$97.70	11.381%	$108.8192	$108.82	$108.80	$108.80
7 purchase totals =	$754.10		$799.2765	$799.28	$799.20	$799.40