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	$222.35	8.112%	$240.387	$240.39	$240.40	$240.40
Purchase #2	$177.98	3.663%	$184.4994	$184.50	$184.50	$184.50
Purchase #3	$230.71	3.332%	$238.3973	$238.40	$238.40	$238.40
Purchase #4	$233.30	12.358%	$262.1312	$262.13	$262.15	$262.10
Purchase #5	$182.66	7.388%	$196.1549	$196.15	$196.15	$196.20
Purchase #6	$89.65	7.518%	$96.3899	$96.39	$96.40	$96.40
Purchase #7	$209.87	12.412%	$235.9191	$235.92	$235.90	$235.90
7 purchase totals =	$1,346.52		$1,453.8788	$1,453.88	$1,453.90	$1,453.90