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	$32.88	13.285%	$37.2481	$37.25	$37.25	$37.20
Purchase #2	$131.65	10.587%	$145.5878	$145.59	$145.60	$145.60
Purchase #3	$194.90	4.714%	$204.0876	$204.09	$204.10	$204.10
Purchase #4	$34.66	9.405%	$37.9198	$37.92	$37.90	$37.90
Purchase #5	$25.37	6.319%	$26.9731	$26.97	$26.95	$27.00
Purchase #6	$54.44	7.738%	$58.6526	$58.65	$58.65	$58.70
Purchase #7	$87.98	3.313%	$90.8948	$90.89	$90.90	$90.90
7 purchase totals =	$561.88		$601.3638	$601.36	$601.35	$601.40