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	$222.39	9.139%	$242.7142	$242.71	$242.70	$242.70
Purchase #2	$169.42	13.160%	$191.7157	$191.72	$191.70	$191.70
Purchase #3	$165.97	9.594%	$181.8932	$181.89	$181.90	$181.90
Purchase #4	$107.37	6.235%	$114.0645	$114.06	$114.05	$114.10
Purchase #5	$212.54	6.343%	$226.0214	$226.02	$226.00	$226.00
Purchase #6	$34.33	10.849%	$38.0545	$38.05	$38.05	$38.10
Purchase #7	$53.82	10.115%	$59.2639	$59.26	$59.25	$59.30
7 purchase totals =	$965.84		$1,053.7274	$1,053.71	$1,053.65	$1,053.80