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	$102.63	8.415%	$111.2663	$111.27	$111.25	$111.30
Purchase #2	$180.73	4.735%	$189.2876	$189.29	$189.30	$189.30
Purchase #3	$101.43	13.208%	$114.8269	$114.83	$114.85	$114.80
Purchase #4	$14.65	5.689%	$15.4834	$15.48	$15.50	$15.50
Purchase #5	$241.87	5.158%	$254.3457	$254.35	$254.35	$254.30
Purchase #6	$227.54	4.488%	$237.752	$237.75	$237.75	$237.80
Purchase #7	$92.55	8.824%	$100.7166	$100.72	$100.70	$100.70
7 purchase totals =	$961.40		$1,023.6785	$1,023.69	$1,023.70	$1,023.70