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	$62.30	8.496%	$67.593	$67.59	$67.60	$67.60
Purchase #2	$147.58	11.482%	$164.5251	$164.53	$164.55	$164.50
Purchase #3	$123.34	6.174%	$130.955	$130.96	$130.95	$131.00
Purchase #4	$31.44	4.796%	$32.9479	$32.95	$32.95	$32.90
Purchase #5	$178.94	6.586%	$190.725	$190.73	$190.75	$190.70
Purchase #6	$151.54	7.374%	$162.7146	$162.71	$162.70	$162.70
Purchase #7	$141.70	8.781%	$154.1427	$154.14	$154.15	$154.10
7 purchase totals =	$836.84		$903.6033	$903.61	$903.65	$903.50