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	$159.95	4.589%	$167.2901	$167.29	$167.30	$167.30
Purchase #2	$94.92	9.696%	$104.1234	$104.12	$104.10	$104.10
Purchase #3	$12.66	4.794%	$13.2669	$13.27	$13.25	$13.30
Purchase #4	$176.30	8.382%	$191.0775	$191.08	$191.10	$191.10
Purchase #5	$86.54	10.124%	$95.3013	$95.30	$95.30	$95.30
Purchase #6	$138.33	9.722%	$151.7784	$151.78	$151.80	$151.80
Purchase #7	$37.31	9.331%	$40.7914	$40.79	$40.80	$40.80
7 purchase totals =	$706.01		$763.6290	$763.63	$763.65	$763.70