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	$166.33	10.125%	$183.1709	$183.17	$183.15	$183.20
Purchase #2	$172.71	9.728%	$189.5112	$189.51	$189.50	$189.50
Purchase #3	$116.39	13.324%	$131.8978	$131.90	$131.90	$131.90
Purchase #4	$245.44	3.237%	$253.3849	$253.38	$253.40	$253.40
Purchase #5	$78.63	8.809%	$85.5565	$85.56	$85.55	$85.60
Purchase #6	$18.88	10.210%	$20.8076	$20.81	$20.80	$20.80
Purchase #7	$156.49	13.410%	$177.4753	$177.48	$177.50	$177.50
7 purchase totals =	$954.87		$1,041.8042	$1,041.81	$1,041.80	$1,041.90