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	$156.39	12.292%	$175.6135	$175.61	$175.60	$175.60
Purchase #2	$157.93	10.446%	$174.4274	$174.43	$174.45	$174.40
Purchase #3	$176.92	10.761%	$195.9584	$195.96	$195.95	$196.00
Purchase #4	$52.56	3.599%	$54.4516	$54.45	$54.45	$54.50
Purchase #5	$56.25	5.269%	$59.2138	$59.21	$59.20	$59.20
Purchase #6	$250.67	3.446%	$259.3081	$259.31	$259.30	$259.30
Purchase #7	$137.60	3.674%	$142.6554	$142.66	$142.65	$142.70
7 purchase totals =	$988.32		$1,061.6282	$1,061.63	$1,061.60	$1,061.70