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	$124.66	10.145%	$137.3068	$137.31	$137.30	$137.30
Purchase #2	$133.48	7.795%	$143.8848	$143.88	$143.90	$143.90
Purchase #3	$163.71	5.360%	$172.4849	$172.48	$172.50	$172.50
Purchase #4	$137.69	7.195%	$147.5968	$147.60	$147.60	$147.60
Purchase #5	$67.97	7.243%	$72.8931	$72.89	$72.90	$72.90
Purchase #6	$240.98	6.148%	$255.7955	$255.80	$255.80	$255.80
Purchase #7	$163.33	11.351%	$181.8696	$181.87	$181.85	$181.90
7 purchase totals =	$1,031.82		$1,111.8315	$1,111.83	$1,111.85	$1,111.90