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	$32.63	5.827%	$34.5314	$34.53	$34.55	$34.50
Purchase #2	$249.29	5.191%	$262.2306	$262.23	$262.25	$262.20
Purchase #3	$115.42	7.326%	$123.8757	$123.88	$123.90	$123.90
Purchase #4	$150.95	9.349%	$165.0623	$165.06	$165.05	$165.10
Purchase #5	$171.44	11.217%	$190.6704	$190.67	$190.65	$190.70
Purchase #6	$138.87	4.619%	$145.2844	$145.28	$145.30	$145.30
Purchase #7	$42.61	5.753%	$45.0614	$45.06	$45.05	$45.10
7 purchase totals =	$901.21		$966.7162	$966.71	$966.75	$966.80