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	$78.33	8.721%	$85.1612	$85.16	$85.15	$85.20
Purchase #2	$105.63	12.783%	$119.1327	$119.13	$119.15	$119.10
Purchase #3	$36.25	3.455%	$37.5024	$37.50	$37.50	$37.50
Purchase #4	$195.39	5.122%	$205.3979	$205.40	$205.40	$205.40
Purchase #5	$197.39	6.606%	$210.4296	$210.43	$210.45	$210.40
Purchase #6	$204.41	11.641%	$228.2054	$228.21	$228.20	$228.20
Purchase #7	$37.60	13.720%	$42.7587	$42.76	$42.75	$42.80
7 purchase totals =	$855.00		$928.5879	$928.59	$928.60	$928.60