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	$155.79	5.853%	$164.9084	$164.91	$164.90	$164.90
Purchase #2	$171.58	7.259%	$184.035	$184.04	$184.05	$184.00
Purchase #3	$142.68	6.593%	$152.0869	$152.09	$152.10	$152.10
Purchase #4	$141.51	10.362%	$156.1733	$156.17	$156.15	$156.20
Purchase #5	$247.77	10.347%	$273.4068	$273.41	$273.40	$273.40
Purchase #6	$218.42	4.138%	$227.4582	$227.46	$227.45	$227.50
Purchase #7	$194.61	10.528%	$215.0985	$215.10	$215.10	$215.10
7 purchase totals =	$1,272.36		$1,373.1671	$1,373.18	$1,373.15	$1,373.20