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	$63.26	6.321%	$67.2587	$67.26	$67.25	$67.30
Purchase #2	$217.98	5.697%	$230.3983	$230.40	$230.40	$230.40
Purchase #3	$216.86	7.602%	$233.3457	$233.35	$233.35	$233.30
Purchase #4	$171.31	4.761%	$179.4661	$179.47	$179.45	$179.50
Purchase #5	$147.74	3.468%	$152.8636	$152.86	$152.85	$152.90
Purchase #6	$218.31	11.125%	$242.597	$242.60	$242.60	$242.60
Purchase #7	$64.50	12.183%	$72.358	$72.36	$72.35	$72.40
7 purchase totals =	$1,099.96		$1,178.2874	$1,178.30	$1,178.25	$1,178.40