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	$235.58	11.606%	$262.9214	$262.92	$262.90	$262.90
Purchase #2	$57.46	5.334%	$60.5249	$60.52	$60.50	$60.50
Purchase #3	$227.31	4.525%	$237.5958	$237.60	$237.60	$237.60
Purchase #4	$154.82	9.501%	$169.5294	$169.53	$169.55	$169.50
Purchase #5	$99.67	11.772%	$111.4032	$111.40	$111.40	$111.40
Purchase #6	$110.28	11.650%	$123.1276	$123.13	$123.15	$123.10
Purchase #7	$119.89	4.317%	$125.0657	$125.07	$125.05	$125.10
7 purchase totals =	$1,005.01		$1,090.1680	$1,090.17	$1,090.15	$1,090.10