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	$10.31	4.163%	$10.7392	$10.74	$10.75	$10.70
Purchase #2	$19.46	10.427%	$21.4891	$21.49	$21.50	$21.50
Purchase #3	$86.86	13.530%	$98.6122	$98.61	$98.60	$98.60
Purchase #4	$12.82	9.371%	$14.0214	$14.02	$14.00	$14.00
Purchase #5	$43.71	8.481%	$47.417	$47.42	$47.40	$47.40
Purchase #6	$196.35	9.668%	$215.3331	$215.33	$215.35	$215.30
Purchase #7	$179.96	6.842%	$192.2729	$192.27	$192.25	$192.30
7 purchase totals =	$549.47		$599.8849	$599.88	$599.85	$599.80