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	$23.94	5.114%	$25.1643	$25.16	$25.15	$25.20
Purchase #2	$168.25	11.841%	$188.1725	$188.17	$188.15	$188.20
Purchase #3	$17.36	6.501%	$18.4886	$18.49	$18.50	$18.50
Purchase #4	$62.59	8.112%	$67.6673	$67.67	$67.65	$67.70
Purchase #5	$242.80	10.711%	$268.8063	$268.81	$268.80	$268.80
Purchase #6	$54.75	12.570%	$61.6321	$61.63	$61.65	$61.60
Purchase #7	$158.87	8.552%	$172.4566	$172.46	$172.45	$172.50
7 purchase totals =	$728.56		$802.3877	$802.39	$802.35	$802.50