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	$198.32	13.103%	$224.3059	$224.31	$224.30	$224.30
Purchase #2	$20.78	4.751%	$21.7673	$21.77	$21.75	$21.80
Purchase #3	$101.55	9.347%	$111.0419	$111.04	$111.05	$111.00
Purchase #4	$21.93	11.865%	$24.532	$24.53	$24.55	$24.50
Purchase #5	$36.77	12.183%	$41.2497	$41.25	$41.25	$41.20
Purchase #6	$78.33	11.775%	$87.5534	$87.55	$87.55	$87.60
Purchase #7	$147.79	13.648%	$167.9604	$167.96	$167.95	$168.00
7 purchase totals =	$605.47		$678.4106	$678.41	$678.40	$678.40