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	$143.64	6.244%	$152.6089	$152.61	$152.60	$152.60
Purchase #2	$48.69	8.377%	$52.7688	$52.77	$52.75	$52.80
Purchase #3	$17.97	11.417%	$20.0216	$20.02	$20.00	$20.00
Purchase #4	$105.81	10.491%	$116.9105	$116.91	$116.90	$116.90
Purchase #5	$206.29	6.414%	$219.5214	$219.52	$219.50	$219.50
Purchase #6	$173.82	3.578%	$180.0393	$180.04	$180.05	$180.00
Purchase #7	$245.91	12.574%	$276.8307	$276.83	$276.85	$276.80
7 purchase totals =	$942.13		$1,018.7012	$1,018.70	$1,018.65	$1,018.60