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	$154.66	6.339%	$164.4639	$164.46	$164.45	$164.50
Purchase #2	$89.81	4.118%	$93.5084	$93.51	$93.50	$93.50
Purchase #3	$215.89	8.218%	$233.6318	$233.63	$233.65	$233.60
Purchase #4	$137.95	9.838%	$151.5215	$151.52	$151.50	$151.50
Purchase #5	$170.73	7.273%	$183.1472	$183.15	$183.15	$183.10
Purchase #6	$216.98	7.790%	$233.8827	$233.88	$233.90	$233.90
Purchase #7	$248.45	10.430%	$274.3633	$274.36	$274.35	$274.40
7 purchase totals =	$1,234.47		$1,334.5188	$1,334.51	$1,334.50	$1,334.50