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	$98.33	11.776%	$109.9093	$109.91	$109.90	$109.90
Purchase #2	$20.72	4.859%	$21.7268	$21.73	$21.75	$21.70
Purchase #3	$45.77	4.698%	$47.9203	$47.92	$47.90	$47.90
Purchase #4	$172.84	6.788%	$184.5724	$184.57	$184.55	$184.60
Purchase #5	$71.26	6.185%	$75.6674	$75.67	$75.65	$75.70
Purchase #6	$28.31	13.498%	$32.1313	$32.13	$32.15	$32.10
Purchase #7	$44.78	13.707%	$50.918	$50.92	$50.90	$50.90
7 purchase totals =	$482.01		$522.8455	$522.85	$522.80	$522.80