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	$49.98	6.330%	$53.1437	$53.14	$53.15	$53.10
Purchase #2	$69.61	10.465%	$76.8947	$76.89	$76.90	$76.90
Purchase #3	$111.83	6.109%	$118.6617	$118.66	$118.65	$118.70
Purchase #4	$20.75	6.165%	$22.0292	$22.03	$22.05	$22.00
Purchase #5	$120.97	12.846%	$136.5098	$136.51	$136.50	$136.50
Purchase #6	$236.85	10.377%	$261.4279	$261.43	$261.45	$261.40
Purchase #7	$159.30	3.486%	$164.8532	$164.85	$164.85	$164.90
7 purchase totals =	$769.29		$833.5202	$833.51	$833.55	$833.50