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	$233.90	8.238%	$253.1687	$253.17	$253.15	$253.20
Purchase #2	$42.53	6.673%	$45.368	$45.37	$45.35	$45.40
Purchase #3	$150.26	12.190%	$168.5767	$168.58	$168.60	$168.60
Purchase #4	$18.98	3.404%	$19.6261	$19.63	$19.65	$19.60
Purchase #5	$80.66	10.543%	$89.164	$89.16	$89.15	$89.20
Purchase #6	$35.54	10.819%	$39.3851	$39.39	$39.40	$39.40
Purchase #7	$192.37	7.688%	$207.1594	$207.16	$207.15	$207.20
7 purchase totals =	$754.24		$822.4480	$822.46	$822.45	$822.60