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	$84.93	4.709%	$88.9294	$88.93	$88.95	$88.90
Purchase #2	$104.86	12.274%	$117.7305	$117.73	$117.75	$117.70
Purchase #3	$35.37	4.852%	$37.0862	$37.09	$37.10	$37.10
Purchase #4	$42.69	10.139%	$47.0183	$47.02	$47.00	$47.00
Purchase #5	$36.89	12.237%	$41.4042	$41.40	$41.40	$41.40
Purchase #6	$57.42	6.465%	$61.1322	$61.13	$61.15	$61.10
Purchase #7	$213.53	13.856%	$243.1167	$243.12	$243.10	$243.10
7 purchase totals =	$575.69		$636.4175	$636.42	$636.45	$636.30