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	$146.64	9.123%	$160.018	$160.02	$160.00	$160.00
Purchase #2	$194.40	11.400%	$216.5616	$216.56	$216.55	$216.60
Purchase #3	$104.64	13.170%	$118.4211	$118.42	$118.40	$118.40
Purchase #4	$157.44	4.637%	$164.7405	$164.74	$164.75	$164.70
Purchase #5	$247.61	7.152%	$265.3191	$265.32	$265.30	$265.30
Purchase #6	$33.54	13.214%	$37.972	$37.97	$37.95	$38.00
Purchase #7	$58.61	6.666%	$62.5169	$62.52	$62.50	$62.50
7 purchase totals =	$942.88		$1,025.5492	$1,025.55	$1,025.45	$1,025.50