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	$88.38	8.419%	$95.8207	$95.82	$95.80	$95.80
Purchase #2	$13.73	11.537%	$15.314	$15.31	$15.30	$15.30
Purchase #3	$194.90	4.812%	$204.2786	$204.28	$204.30	$204.30
Purchase #4	$58.52	6.539%	$62.3466	$62.35	$62.35	$62.30
Purchase #5	$172.34	7.279%	$184.8846	$184.88	$184.90	$184.90
Purchase #6	$233.82	3.712%	$242.4994	$242.50	$242.50	$242.50
Purchase #7	$179.31	10.159%	$197.5261	$197.53	$197.55	$197.50
7 purchase totals =	$941.00		$1,002.6700	$1,002.67	$1,002.70	$1,002.60