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	$184.67	8.258%	$199.92	$199.92	$199.90	$199.90
Purchase #2	$154.54	6.349%	$164.3517	$164.35	$164.35	$164.40
Purchase #3	$76.77	11.118%	$85.3053	$85.31	$85.30	$85.30
Purchase #4	$47.77	13.783%	$54.3541	$54.35	$54.35	$54.40
Purchase #5	$70.46	3.204%	$72.7175	$72.72	$72.70	$72.70
Purchase #6	$136.98	9.673%	$150.2301	$150.23	$150.25	$150.20
Purchase #7	$20.31	7.224%	$21.7772	$21.78	$21.80	$21.80
7 purchase totals =	$691.50		$748.6559	$748.66	$748.65	$748.70