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	$9.37	13.420%	$10.6275	$10.63	$10.65	$10.60
Purchase #2	$152.29	8.626%	$165.4265	$165.43	$165.45	$165.40
Purchase #3	$40.79	13.471%	$46.2848	$46.28	$46.30	$46.30
Purchase #4	$114.92	3.851%	$119.3456	$119.35	$119.35	$119.30
Purchase #5	$116.74	9.179%	$127.4556	$127.46	$127.45	$127.50
Purchase #6	$28.55	11.460%	$31.8218	$31.82	$31.80	$31.80
Purchase #7	$179.80	6.422%	$191.3468	$191.35	$191.35	$191.30
7 purchase totals =	$642.46		$692.3086	$692.32	$692.35	$692.20