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	$142.72	13.663%	$162.2198	$162.22	$162.20	$162.20
Purchase #2	$207.77	3.301%	$214.6285	$214.63	$214.65	$214.60
Purchase #3	$38.50	13.272%	$43.6097	$43.61	$43.60	$43.60
Purchase #4	$57.95	6.276%	$61.5869	$61.59	$61.60	$61.60
Purchase #5	$52.53	9.226%	$57.3764	$57.38	$57.40	$57.40
Purchase #6	$135.29	11.226%	$150.4777	$150.48	$150.50	$150.50
Purchase #7	$50.59	8.578%	$54.9296	$54.93	$54.95	$54.90
7 purchase totals =	$685.35		$744.8286	$744.84	$744.90	$744.80