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	$94.33	6.548%	$100.5067	$100.51	$100.50	$100.50
Purchase #2	$40.29	5.336%	$42.4399	$42.44	$42.45	$42.40
Purchase #3	$199.61	12.297%	$224.156	$224.16	$224.15	$224.20
Purchase #4	$183.42	3.860%	$190.5	$190.50	$190.50	$190.50
Purchase #5	$65.83	10.385%	$72.6664	$72.67	$72.65	$72.70
Purchase #6	$223.75	11.465%	$249.4029	$249.40	$249.40	$249.40
Purchase #7	$126.95	9.769%	$139.3517	$139.35	$139.35	$139.40
7 purchase totals =	$934.18		$1,019.0236	$1,019.03	$1,019.00	$1,019.10