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	$212.55	5.454%	$224.1425	$224.14	$224.15	$224.10
Purchase #2	$174.68	5.533%	$184.345	$184.35	$184.35	$184.30
Purchase #3	$110.77	7.348%	$118.9094	$118.91	$118.90	$118.90
Purchase #4	$114.49	13.373%	$129.8007	$129.80	$129.80	$129.80
Purchase #5	$82.60	6.665%	$88.1053	$88.11	$88.10	$88.10
Purchase #6	$100.85	5.710%	$106.6085	$106.61	$106.60	$106.60
Purchase #7	$141.89	6.146%	$150.6106	$150.61	$150.60	$150.60
7 purchase totals =	$937.83		$1,002.5220	$1,002.53	$1,002.50	$1,002.40