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	$84.32	7.617%	$90.7427	$90.74	$90.75	$90.70
Purchase #2	$83.29	3.742%	$86.4067	$86.41	$86.40	$86.40
Purchase #3	$40.77	10.591%	$45.088	$45.09	$45.10	$45.10
Purchase #4	$54.27	12.629%	$61.1238	$61.12	$61.10	$61.10
Purchase #5	$65.40	13.863%	$74.4664	$74.47	$74.45	$74.50
Purchase #6	$79.82	7.865%	$86.0978	$86.10	$86.10	$86.10
Purchase #7	$50.54	3.406%	$52.2614	$52.26	$52.25	$52.30
7 purchase totals =	$458.41		$496.1868	$496.19	$496.15	$496.20