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	$65.60	5.731%	$69.3595	$69.36	$69.35	$69.40
Purchase #2	$116.36	12.220%	$130.5792	$130.58	$130.60	$130.60
Purchase #3	$54.56	4.261%	$56.8848	$56.88	$56.90	$56.90
Purchase #4	$196.41	10.519%	$217.0704	$217.07	$217.05	$217.10
Purchase #5	$217.86	6.720%	$232.5002	$232.50	$232.50	$232.50
Purchase #6	$135.59	6.377%	$144.2366	$144.24	$144.25	$144.20
Purchase #7	$86.29	5.214%	$90.7892	$90.79	$90.80	$90.80
7 purchase totals =	$872.67		$941.4199	$941.42	$941.45	$941.50