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	$197.62	9.458%	$216.3109	$216.31	$216.30	$216.30
Purchase #2	$87.98	3.190%	$90.7866	$90.79	$90.80	$90.80
Purchase #3	$133.90	9.110%	$146.0983	$146.10	$146.10	$146.10
Purchase #4	$93.98	6.226%	$99.8312	$99.83	$99.85	$99.80
Purchase #5	$72.70	13.583%	$82.5748	$82.57	$82.55	$82.60
Purchase #6	$53.30	6.765%	$56.9057	$56.91	$56.90	$56.90
Purchase #7	$65.53	13.690%	$74.5011	$74.50	$74.50	$74.50
7 purchase totals =	$705.01		$767.0086	$767.01	$767.00	$767.00