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	$245.49	12.220%	$275.4889	$275.49	$275.50	$275.50
Purchase #2	$11.64	3.679%	$12.0682	$12.07	$12.05	$12.10
Purchase #3	$142.43	8.502%	$154.5394	$154.54	$154.55	$154.50
Purchase #4	$90.53	9.805%	$99.4065	$99.41	$99.40	$99.40
Purchase #5	$168.96	3.121%	$174.2332	$174.23	$174.25	$174.20
Purchase #6	$131.90	13.860%	$150.1813	$150.18	$150.20	$150.20
Purchase #7	$91.35	7.241%	$97.9647	$97.96	$97.95	$98.00
7 purchase totals =	$882.30		$963.8822	$963.88	$963.90	$963.90