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	$61.84	10.145%	$68.1137	$68.11	$68.10	$68.10
Purchase #2	$236.92	13.302%	$268.4351	$268.44	$268.45	$268.40
Purchase #3	$222.76	11.140%	$247.5755	$247.58	$247.60	$247.60
Purchase #4	$100.60	13.847%	$114.5301	$114.53	$114.55	$114.50
Purchase #5	$156.85	6.205%	$166.5825	$166.58	$166.60	$166.60
Purchase #6	$34.31	10.542%	$37.927	$37.93	$37.95	$37.90
Purchase #7	$186.79	7.268%	$200.3659	$200.37	$200.35	$200.40
7 purchase totals =	$1,000.07		$1,103.5298	$1,103.54	$1,103.60	$1,103.50