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	$162.61	12.841%	$183.4908	$183.49	$183.50	$183.50
Purchase #2	$67.63	5.554%	$71.3862	$71.39	$71.40	$71.40
Purchase #3	$42.34	3.147%	$43.6724	$43.67	$43.65	$43.70
Purchase #4	$121.70	11.817%	$136.0813	$136.08	$136.10	$136.10
Purchase #5	$218.72	7.256%	$234.5903	$234.59	$234.60	$234.60
Purchase #6	$91.63	3.624%	$94.9507	$94.95	$94.95	$95.00
Purchase #7	$219.40	12.658%	$247.1717	$247.17	$247.15	$247.20
7 purchase totals =	$924.03		$1,011.3434	$1,011.34	$1,011.35	$1,011.50