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	$172.31	7.533%	$185.2901	$185.29	$185.30	$185.30
Purchase #2	$158.25	9.364%	$173.0685	$173.07	$173.05	$173.10
Purchase #3	$153.56	13.525%	$174.329	$174.33	$174.35	$174.30
Purchase #4	$153.47	9.864%	$168.6083	$168.61	$168.60	$168.60
Purchase #5	$35.71	6.627%	$38.0765	$38.08	$38.10	$38.10
Purchase #6	$201.57	5.283%	$212.2189	$212.22	$212.20	$212.20
Purchase #7	$190.87	5.247%	$200.8849	$200.88	$200.90	$200.90
7 purchase totals =	$1,065.74		$1,152.4762	$1,152.48	$1,152.50	$1,152.50