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	$41.70	7.723%	$44.9205	$44.92	$44.90	$44.90
Purchase #2	$165.94	8.668%	$180.3237	$180.32	$180.30	$180.30
Purchase #3	$217.86	6.141%	$231.2388	$231.24	$231.25	$231.20
Purchase #4	$47.86	5.669%	$50.5732	$50.57	$50.55	$50.60
Purchase #5	$66.66	10.461%	$73.6333	$73.63	$73.65	$73.60
Purchase #6	$211.75	4.607%	$221.5053	$221.51	$221.50	$221.50
Purchase #7	$175.97	13.811%	$200.2732	$200.27	$200.25	$200.30
7 purchase totals =	$927.74		$1,002.4680	$1,002.46	$1,002.40	$1,002.40