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	$65.44	10.680%	$72.429	$72.43	$72.45	$72.40
Purchase #2	$227.46	4.857%	$238.5077	$238.51	$238.50	$238.50
Purchase #3	$148.67	3.148%	$153.3501	$153.35	$153.35	$153.40
Purchase #4	$103.84	13.723%	$118.09	$118.09	$118.10	$118.10
Purchase #5	$44.79	4.279%	$46.7066	$46.71	$46.70	$46.70
Purchase #6	$249.32	10.298%	$274.995	$275.00	$275.00	$275.00
Purchase #7	$229.56	6.199%	$243.7904	$243.79	$243.80	$243.80
7 purchase totals =	$1,069.08		$1,147.8688	$1,147.88	$1,147.90	$1,147.90