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	$159.66	3.321%	$164.9623	$164.96	$164.95	$165.00
Purchase #2	$152.59	10.573%	$168.7233	$168.72	$168.70	$168.70
Purchase #3	$123.38	5.565%	$130.2461	$130.25	$130.25	$130.20
Purchase #4	$40.29	7.485%	$43.3057	$43.31	$43.30	$43.30
Purchase #5	$201.39	6.182%	$213.8399	$213.84	$213.85	$213.80
Purchase #6	$167.39	3.245%	$172.8218	$172.82	$172.80	$172.80
Purchase #7	$140.32	7.362%	$150.6504	$150.65	$150.65	$150.70
7 purchase totals =	$985.02		$1,044.5495	$1,044.55	$1,044.50	$1,044.50