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	$64.68	3.551%	$66.9768	$66.98	$67.00	$67.00
Purchase #2	$237.77	6.872%	$254.1096	$254.11	$254.10	$254.10
Purchase #3	$249.53	3.642%	$258.6179	$258.62	$258.60	$258.60
Purchase #4	$183.65	8.666%	$199.5651	$199.57	$199.55	$199.60
Purchase #5	$40.52	3.865%	$42.0861	$42.09	$42.10	$42.10
Purchase #6	$143.32	6.167%	$152.1585	$152.16	$152.15	$152.20
Purchase #7	$59.91	11.138%	$66.5828	$66.58	$66.60	$66.60
7 purchase totals =	$979.38		$1,040.0968	$1,040.11	$1,040.10	$1,040.20