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	$131.43	8.725%	$142.8973	$142.90	$142.90	$142.90
Purchase #2	$10.80	9.312%	$11.8057	$11.81	$11.80	$11.80
Purchase #3	$220.71	13.301%	$250.0666	$250.07	$250.05	$250.10
Purchase #4	$52.77	13.302%	$59.7895	$59.79	$59.80	$59.80
Purchase #5	$196.75	6.459%	$209.4581	$209.46	$209.45	$209.50
Purchase #6	$116.30	10.696%	$128.7394	$128.74	$128.75	$128.70
Purchase #7	$25.44	9.576%	$27.8761	$27.88	$27.90	$27.90
7 purchase totals =	$754.20		$830.6327	$830.65	$830.65	$830.70