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	$152.94	3.285%	$157.9641	$157.96	$157.95	$158.00
Purchase #2	$140.63	6.298%	$149.4869	$149.49	$149.50	$149.50
Purchase #3	$214.33	11.240%	$238.4207	$238.42	$238.40	$238.40
Purchase #4	$73.67	13.679%	$83.7473	$83.75	$83.75	$83.70
Purchase #5	$62.87	8.609%	$68.2825	$68.28	$68.30	$68.30
Purchase #6	$110.25	8.470%	$119.5882	$119.59	$119.60	$119.60
Purchase #7	$179.56	11.600%	$200.389	$200.39	$200.40	$200.40
7 purchase totals =	$934.25		$1,017.8787	$1,017.88	$1,017.90	$1,017.90