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	$179.26	8.590%	$194.6584	$194.66	$194.65	$194.70
Purchase #2	$137.89	8.859%	$150.1057	$150.11	$150.10	$150.10
Purchase #3	$136.28	6.754%	$145.4844	$145.48	$145.50	$145.50
Purchase #4	$37.84	13.421%	$42.9185	$42.92	$42.90	$42.90
Purchase #5	$172.75	6.777%	$184.4573	$184.46	$184.45	$184.50
Purchase #6	$116.29	12.814%	$131.1914	$131.19	$131.20	$131.20
Purchase #7	$27.27	12.119%	$30.5749	$30.57	$30.55	$30.60
7 purchase totals =	$807.58		$879.3906	$879.39	$879.35	$879.50