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	$136.41	11.410%	$151.9744	$151.97	$151.95	$152.00
Purchase #2	$46.61	5.737%	$49.284	$49.28	$49.30	$49.30
Purchase #3	$54.98	10.277%	$60.6303	$60.63	$60.65	$60.60
Purchase #4	$115.28	6.791%	$123.1087	$123.11	$123.10	$123.10
Purchase #5	$84.55	5.835%	$89.4835	$89.48	$89.50	$89.50
Purchase #6	$177.31	8.195%	$191.8406	$191.84	$191.85	$191.80
Purchase #7	$189.31	5.606%	$199.9227	$199.92	$199.90	$199.90
7 purchase totals =	$804.45		$866.2442	$866.23	$866.25	$866.20