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	$90.26	9.184%	$98.5495	$98.55	$98.55	$98.50
Purchase #2	$169.39	3.400%	$175.1493	$175.15	$175.15	$175.10
Purchase #3	$121.76	9.336%	$133.1275	$133.13	$133.15	$133.10
Purchase #4	$246.79	13.145%	$279.2305	$279.23	$279.25	$279.20
Purchase #5	$242.35	12.365%	$272.3166	$272.32	$272.30	$272.30
Purchase #6	$64.54	10.156%	$71.0947	$71.09	$71.10	$71.10
Purchase #7	$142.50	9.424%	$155.9292	$155.93	$155.95	$155.90
7 purchase totals =	$1,077.59		$1,185.3973	$1,185.40	$1,185.45	$1,185.20