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	$176.41	12.300%	$198.1084	$198.11	$198.10	$198.10
Purchase #2	$49.44	8.394%	$53.59	$53.59	$53.60	$53.60
Purchase #3	$52.44	13.588%	$59.5655	$59.57	$59.55	$59.60
Purchase #4	$80.53	13.152%	$91.1213	$91.12	$91.10	$91.10
Purchase #5	$59.30	7.314%	$63.6372	$63.64	$63.65	$63.60
Purchase #6	$131.50	8.327%	$142.45	$142.45	$142.45	$142.50
Purchase #7	$216.65	5.349%	$228.2386	$228.24	$228.25	$228.20
7 purchase totals =	$766.27		$836.7110	$836.72	$836.70	$836.70