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	$60.48	8.476%	$65.6063	$65.61	$65.60	$65.60
Purchase #2	$180.58	12.337%	$202.8582	$202.86	$202.85	$202.90
Purchase #3	$126.63	12.764%	$142.7931	$142.79	$142.80	$142.80
Purchase #4	$149.99	5.439%	$158.148	$158.15	$158.15	$158.10
Purchase #5	$34.90	7.864%	$37.6445	$37.64	$37.65	$37.60
Purchase #6	$222.78	10.172%	$245.4412	$245.44	$245.45	$245.40
Purchase #7	$80.37	6.854%	$85.8786	$85.88	$85.90	$85.90
7 purchase totals =	$855.73		$938.3699	$938.37	$938.40	$938.30