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	$90.72	6.339%	$96.4707	$96.47	$96.45	$96.50
Purchase #2	$250.78	3.579%	$259.7554	$259.76	$259.75	$259.80
Purchase #3	$156.92	13.546%	$178.1764	$178.18	$178.20	$178.20
Purchase #4	$109.68	12.551%	$123.4459	$123.45	$123.45	$123.40
Purchase #5	$76.86	9.211%	$83.9396	$83.94	$83.95	$83.90
Purchase #6	$216.61	3.388%	$223.9487	$223.95	$223.95	$223.90
Purchase #7	$65.44	12.563%	$73.6612	$73.66	$73.65	$73.70
7 purchase totals =	$967.01		$1,039.3979	$1,039.41	$1,039.40	$1,039.40