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	$144.64	5.563%	$152.6863	$152.69	$152.70	$152.70
Purchase #2	$169.72	9.341%	$185.5735	$185.57	$185.55	$185.60
Purchase #3	$65.60	9.831%	$72.0491	$72.05	$72.05	$72.00
Purchase #4	$138.81	7.231%	$148.8474	$148.85	$148.85	$148.80
Purchase #5	$81.95	4.227%	$85.414	$85.41	$85.40	$85.40
Purchase #6	$169.31	6.441%	$180.2153	$180.22	$180.20	$180.20
Purchase #7	$54.74	11.194%	$60.8676	$60.87	$60.85	$60.90
7 purchase totals =	$824.77		$885.6532	$885.66	$885.60	$885.60