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	$119.28	7.837%	$128.628	$128.63	$128.65	$128.60
Purchase #2	$80.58	11.862%	$90.1384	$90.14	$90.15	$90.10
Purchase #3	$147.97	11.488%	$164.9688	$164.97	$164.95	$165.00
Purchase #4	$9.64	6.869%	$10.3022	$10.30	$10.30	$10.30
Purchase #5	$143.47	6.454%	$152.7296	$152.73	$152.75	$152.70
Purchase #6	$215.83	10.390%	$238.2547	$238.25	$238.25	$238.30
Purchase #7	$161.41	7.443%	$173.4237	$173.42	$173.40	$173.40
7 purchase totals =	$878.18		$958.4454	$958.44	$958.45	$958.40