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	$103.97	7.279%	$111.538	$111.54	$111.55	$111.50
Purchase #2	$232.62	9.753%	$255.3074	$255.31	$255.30	$255.30
Purchase #3	$155.55	12.151%	$174.4509	$174.45	$174.45	$174.50
Purchase #4	$191.84	9.186%	$209.4624	$209.46	$209.45	$209.50
Purchase #5	$229.49	5.183%	$241.3845	$241.38	$241.40	$241.40
Purchase #6	$135.42	12.527%	$152.3841	$152.38	$152.40	$152.40
Purchase #7	$197.42	3.644%	$204.614	$204.61	$204.60	$204.60
7 purchase totals =	$1,246.31		$1,349.1413	$1,349.13	$1,349.15	$1,349.20