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	$192.87	6.103%	$204.6409	$204.64	$204.65	$204.60
Purchase #2	$146.47	3.431%	$151.4954	$151.50	$151.50	$151.50
Purchase #3	$69.29	11.841%	$77.4946	$77.49	$77.50	$77.50
Purchase #4	$80.43	11.826%	$89.9417	$89.94	$89.95	$89.90
Purchase #5	$134.69	7.180%	$144.3607	$144.36	$144.35	$144.40
Purchase #6	$180.45	11.851%	$201.8351	$201.84	$201.85	$201.80
Purchase #7	$156.69	9.368%	$171.3687	$171.37	$171.35	$171.40
7 purchase totals =	$960.89		$1,041.1371	$1,041.14	$1,041.15	$1,041.10