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	$28.47	10.415%	$31.4352	$31.44	$31.45	$31.40
Purchase #2	$164.62	3.502%	$170.385	$170.39	$170.40	$170.40
Purchase #3	$191.53	4.721%	$200.5721	$200.57	$200.55	$200.60
Purchase #4	$100.58	8.104%	$108.731	$108.73	$108.75	$108.70
Purchase #5	$179.91	13.113%	$203.5016	$203.50	$203.50	$203.50
Purchase #6	$244.87	4.274%	$255.3357	$255.34	$255.35	$255.30
Purchase #7	$128.57	10.251%	$141.7497	$141.75	$141.75	$141.70
7 purchase totals =	$1,038.55		$1,111.7103	$1,111.72	$1,111.75	$1,111.60