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	$172.78	9.344%	$188.9246	$188.92	$188.90	$188.90
Purchase #2	$37.31	13.497%	$42.3457	$42.35	$42.35	$42.30
Purchase #3	$232.76	12.780%	$262.5067	$262.51	$262.50	$262.50
Purchase #4	$118.31	5.269%	$124.5438	$124.54	$124.55	$124.50
Purchase #5	$64.55	5.567%	$68.1435	$68.14	$68.15	$68.10
Purchase #6	$184.91	11.643%	$206.4391	$206.44	$206.45	$206.40
Purchase #7	$103.82	7.643%	$111.755	$111.76	$111.75	$111.80
7 purchase totals =	$914.44		$1,004.6584	$1,004.66	$1,004.65	$1,004.50