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	$36.84	6.524%	$39.2434	$39.24	$39.25	$39.20
Purchase #2	$132.78	10.557%	$146.7976	$146.80	$146.80	$146.80
Purchase #3	$140.37	9.720%	$154.014	$154.01	$154.00	$154.00
Purchase #4	$198.55	6.621%	$211.696	$211.70	$211.70	$211.70
Purchase #5	$53.46	11.849%	$59.7945	$59.79	$59.80	$59.80
Purchase #6	$217.78	11.489%	$242.8007	$242.80	$242.80	$242.80
Purchase #7	$240.43	6.763%	$256.6903	$256.69	$256.70	$256.70
7 purchase totals =	$1,020.21		$1,111.0365	$1,111.03	$1,111.05	$1,111.00