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	$162.44	3.777%	$168.5754	$168.58	$168.60	$168.60
Purchase #2	$89.37	3.632%	$92.6159	$92.62	$92.60	$92.60
Purchase #3	$73.71	13.731%	$83.8311	$83.83	$83.85	$83.80
Purchase #4	$95.33	12.139%	$106.9021	$106.90	$106.90	$106.90
Purchase #5	$179.97	6.262%	$191.2397	$191.24	$191.25	$191.20
Purchase #6	$35.28	5.416%	$37.1908	$37.19	$37.20	$37.20
Purchase #7	$78.90	8.574%	$85.6649	$85.66	$85.65	$85.70
7 purchase totals =	$715.00		$766.0199	$766.02	$766.05	$766.00