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	$100.72	10.603%	$111.3993	$111.40	$111.40	$111.40
Purchase #2	$105.60	6.775%	$112.7544	$112.75	$112.75	$112.80
Purchase #3	$109.41	11.221%	$121.6869	$121.69	$121.70	$121.70
Purchase #4	$144.95	7.223%	$155.4197	$155.42	$155.40	$155.40
Purchase #5	$236.60	10.669%	$261.8429	$261.84	$261.85	$261.80
Purchase #6	$100.89	10.116%	$111.096	$111.10	$111.10	$111.10
Purchase #7	$48.40	10.653%	$53.5561	$53.56	$53.55	$53.60
7 purchase totals =	$846.57		$927.7553	$927.76	$927.75	$927.80