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	$198.30	12.260%	$222.6116	$222.61	$222.60	$222.60
Purchase #2	$6.37	6.506%	$6.7844	$6.78	$6.80	$6.80
Purchase #3	$152.92	8.661%	$166.1644	$166.16	$166.15	$166.20
Purchase #4	$152.25	7.764%	$164.0707	$164.07	$164.05	$164.10
Purchase #5	$19.26	5.202%	$20.2619	$20.26	$20.25	$20.30
Purchase #6	$237.60	13.580%	$269.8661	$269.87	$269.85	$269.90
Purchase #7	$230.42	5.561%	$243.2337	$243.23	$243.25	$243.20
7 purchase totals =	$997.12		$1,092.9928	$1,092.98	$1,092.95	$1,093.10