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	$110.56	3.275%	$114.1808	$114.18	$114.20	$114.20
Purchase #2	$175.70	8.674%	$190.9402	$190.94	$190.95	$190.90
Purchase #3	$165.53	3.303%	$170.9975	$171.00	$171.00	$171.00
Purchase #4	$97.67	3.260%	$100.854	$100.85	$100.85	$100.90
Purchase #5	$176.46	12.509%	$198.5334	$198.53	$198.55	$198.50
Purchase #6	$246.96	3.711%	$256.1247	$256.12	$256.10	$256.10
Purchase #7	$245.84	9.640%	$269.539	$269.54	$269.55	$269.50
7 purchase totals =	$1,218.72		$1,301.1696	$1,301.16	$1,301.20	$1,301.10