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	$119.37	6.641%	$127.2974	$127.30	$127.30	$127.30
Purchase #2	$45.85	9.423%	$50.1704	$50.17	$50.15	$50.20
Purchase #3	$183.54	8.282%	$198.7408	$198.74	$198.75	$198.70
Purchase #4	$176.71	11.199%	$196.4998	$196.50	$196.50	$196.50
Purchase #5	$191.45	4.688%	$200.4252	$200.43	$200.45	$200.40
Purchase #6	$153.65	7.746%	$165.5517	$165.55	$165.55	$165.60
Purchase #7	$202.45	8.119%	$218.8869	$218.89	$218.90	$218.90
7 purchase totals =	$1,073.02		$1,157.5722	$1,157.58	$1,157.60	$1,157.60