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	$214.33	13.608%	$243.496	$243.50	$243.50	$243.50
Purchase #2	$70.58	3.626%	$73.1392	$73.14	$73.15	$73.10
Purchase #3	$246.76	3.697%	$255.8827	$255.88	$255.90	$255.90
Purchase #4	$21.61	7.490%	$23.2286	$23.23	$23.25	$23.20
Purchase #5	$156.37	3.384%	$161.6616	$161.66	$161.65	$161.70
Purchase #6	$166.27	7.152%	$178.1616	$178.16	$178.15	$178.20
Purchase #7	$37.56	7.320%	$40.3094	$40.31	$40.30	$40.30
7 purchase totals =	$913.48		$975.8791	$975.88	$975.90	$975.90