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	$214.98	8.264%	$232.7459	$232.75	$232.75	$232.70
Purchase #2	$31.52	7.417%	$33.8578	$33.86	$33.85	$33.90
Purchase #3	$161.50	3.743%	$167.5449	$167.54	$167.55	$167.50
Purchase #4	$29.61	10.227%	$32.6382	$32.64	$32.65	$32.60
Purchase #5	$72.37	8.658%	$78.6358	$78.64	$78.65	$78.60
Purchase #6	$36.76	7.784%	$39.6214	$39.62	$39.60	$39.60
Purchase #7	$79.79	7.164%	$85.5062	$85.51	$85.50	$85.50
7 purchase totals =	$626.53		$670.5502	$670.56	$670.55	$670.40