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	$95.47	10.678%	$105.6643	$105.66	$105.65	$105.70
Purchase #2	$239.28	3.489%	$247.6285	$247.63	$247.65	$247.60
Purchase #3	$136.31	12.170%	$152.8989	$152.90	$152.90	$152.90
Purchase #4	$207.25	4.517%	$216.6115	$216.61	$216.60	$216.60
Purchase #5	$222.95	8.718%	$242.3868	$242.39	$242.40	$242.40
Purchase #6	$71.90	13.148%	$81.3534	$81.35	$81.35	$81.40
Purchase #7	$179.66	6.786%	$191.8517	$191.85	$191.85	$191.90
7 purchase totals =	$1,152.82		$1,238.3951	$1,238.39	$1,238.40	$1,238.50