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	$69.28	10.747%	$76.7255	$76.73	$76.75	$76.70
Purchase #2	$57.34	4.550%	$59.949	$59.95	$59.95	$59.90
Purchase #3	$186.94	13.190%	$211.5974	$211.60	$211.60	$211.60
Purchase #4	$89.27	11.158%	$99.2307	$99.23	$99.25	$99.20
Purchase #5	$76.80	7.113%	$82.2628	$82.26	$82.25	$82.30
Purchase #6	$230.99	7.221%	$247.6698	$247.67	$247.65	$247.70
Purchase #7	$244.47	12.859%	$275.9064	$275.91	$275.90	$275.90
7 purchase totals =	$955.09		$1,053.3416	$1,053.35	$1,053.35	$1,053.30