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	$98.73	4.242%	$102.9181	$102.92	$102.90	$102.90
Purchase #2	$119.39	8.571%	$129.6229	$129.62	$129.60	$129.60
Purchase #3	$222.47	4.131%	$231.6602	$231.66	$231.65	$231.70
Purchase #4	$102.69	6.427%	$109.2899	$109.29	$109.30	$109.30
Purchase #5	$40.37	11.499%	$45.0121	$45.01	$45.00	$45.00
Purchase #6	$191.37	4.434%	$199.8553	$199.86	$199.85	$199.90
Purchase #7	$62.93	7.393%	$67.5824	$67.58	$67.60	$67.60
7 purchase totals =	$837.95		$885.9409	$885.94	$885.90	$886.00