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	$125.80	13.652%	$142.9742	$142.97	$142.95	$143.00
Purchase #2	$58.28	7.209%	$62.4814	$62.48	$62.50	$62.50
Purchase #3	$142.30	3.592%	$147.4114	$147.41	$147.40	$147.40
Purchase #4	$53.44	11.130%	$59.3879	$59.39	$59.40	$59.40
Purchase #5	$136.28	11.609%	$152.1007	$152.10	$152.10	$152.10
Purchase #6	$203.59	5.165%	$214.1054	$214.11	$214.10	$214.10
Purchase #7	$197.46	3.546%	$204.4619	$204.46	$204.45	$204.50
7 purchase totals =	$917.15		$982.9229	$982.92	$982.90	$983.00