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	$91.62	11.466%	$102.1251	$102.13	$102.15	$102.10
Purchase #2	$16.73	11.618%	$18.6737	$18.67	$18.65	$18.70
Purchase #3	$73.80	6.422%	$78.5394	$78.54	$78.55	$78.50
Purchase #4	$121.74	12.823%	$137.3507	$137.35	$137.35	$137.40
Purchase #5	$88.48	12.418%	$99.4674	$99.47	$99.45	$99.50
Purchase #6	$97.41	12.162%	$109.257	$109.26	$109.25	$109.30
Purchase #7	$141.77	3.667%	$146.9687	$146.97	$146.95	$147.00
7 purchase totals =	$631.55		$692.3820	$692.39	$692.35	$692.50