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	$102.92	4.261%	$107.3054	$107.31	$107.30	$107.30
Purchase #2	$40.28	4.367%	$42.039	$42.04	$42.05	$42.00
Purchase #3	$101.72	7.838%	$109.6928	$109.69	$109.70	$109.70
Purchase #4	$94.32	11.750%	$105.4026	$105.40	$105.40	$105.40
Purchase #5	$87.82	10.449%	$96.9963	$97.00	$97.00	$97.00
Purchase #6	$214.35	10.649%	$237.1761	$237.18	$237.20	$237.20
Purchase #7	$200.41	10.718%	$221.8899	$221.89	$221.90	$221.90
7 purchase totals =	$841.82		$920.5021	$920.51	$920.55	$920.50