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	$10.38	13.230%	$11.7533	$11.75	$11.75	$11.80
Purchase #2	$63.39	13.150%	$71.7258	$71.73	$71.75	$71.70
Purchase #3	$247.41	6.436%	$263.3333	$263.33	$263.35	$263.30
Purchase #4	$63.97	13.514%	$72.6149	$72.61	$72.60	$72.60
Purchase #5	$244.93	3.297%	$253.0053	$253.01	$253.00	$253.00
Purchase #6	$80.53	13.171%	$91.1366	$91.14	$91.15	$91.10
Purchase #7	$131.60	9.443%	$144.027	$144.03	$144.05	$144.00
7 purchase totals =	$842.21		$907.5962	$907.60	$907.65	$907.50