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	$55.81	6.330%	$59.3428	$59.34	$59.35	$59.30
Purchase #2	$33.31	5.251%	$35.0591	$35.06	$35.05	$35.10
Purchase #3	$236.84	7.358%	$254.2667	$254.27	$254.25	$254.30
Purchase #4	$241.93	9.104%	$263.9553	$263.96	$263.95	$264.00
Purchase #5	$151.56	13.872%	$172.5844	$172.58	$172.60	$172.60
Purchase #6	$182.64	11.384%	$203.4317	$203.43	$203.45	$203.40
Purchase #7	$69.49	12.871%	$78.4341	$78.43	$78.45	$78.40
7 purchase totals =	$971.58		$1,067.0741	$1,067.07	$1,067.10	$1,067.10