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	$169.86	10.570%	$187.8142	$187.81	$187.80	$187.80
Purchase #2	$14.78	4.543%	$15.4515	$15.45	$15.45	$15.50
Purchase #3	$29.75	9.327%	$32.5248	$32.52	$32.50	$32.50
Purchase #4	$235.61	11.727%	$263.24	$263.24	$263.25	$263.20
Purchase #5	$33.76	3.346%	$34.8896	$34.89	$34.90	$34.90
Purchase #6	$173.80	10.175%	$191.4842	$191.48	$191.50	$191.50
Purchase #7	$226.56	11.174%	$251.8758	$251.88	$251.90	$251.90
7 purchase totals =	$884.12		$977.2801	$977.27	$977.30	$977.30