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	$129.37	5.468%	$136.444	$136.44	$136.45	$136.40
Purchase #2	$98.78	12.859%	$111.4821	$111.48	$111.50	$111.50
Purchase #3	$113.96	8.120%	$123.2136	$123.21	$123.20	$123.20
Purchase #4	$50.51	13.803%	$57.4819	$57.48	$57.50	$57.50
Purchase #5	$9.73	6.228%	$10.336	$10.34	$10.35	$10.30
Purchase #6	$243.69	4.289%	$254.1419	$254.14	$254.15	$254.10
Purchase #7	$49.42	7.556%	$53.1542	$53.15	$53.15	$53.20
7 purchase totals =	$695.46		$746.2537	$746.24	$746.30	$746.20