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	$38.99	5.478%	$41.1259	$41.13	$41.15	$41.10
Purchase #2	$216.94	7.665%	$233.5685	$233.57	$233.55	$233.60
Purchase #3	$170.82	10.610%	$188.944	$188.94	$188.95	$188.90
Purchase #4	$192.48	4.369%	$200.8895	$200.89	$200.90	$200.90
Purchase #5	$173.27	7.318%	$185.9499	$185.95	$185.95	$185.90
Purchase #6	$50.90	6.490%	$54.2034	$54.20	$54.20	$54.20
Purchase #7	$189.88	13.469%	$215.4549	$215.45	$215.45	$215.50
7 purchase totals =	$1,033.28		$1,120.1361	$1,120.13	$1,120.15	$1,120.10