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	$55.98	6.523%	$59.6316	$59.63	$59.65	$59.60
Purchase #2	$5.46	4.868%	$5.7258	$5.73	$5.75	$5.70
Purchase #3	$60.38	12.737%	$68.0706	$68.07	$68.05	$68.10
Purchase #4	$72.38	4.460%	$75.6081	$75.61	$75.60	$75.60
Purchase #5	$81.76	7.129%	$87.5887	$87.59	$87.60	$87.60
Purchase #6	$105.42	5.766%	$111.4985	$111.50	$111.50	$111.50
Purchase #7	$154.46	12.708%	$174.0888	$174.09	$174.10	$174.10
7 purchase totals =	$535.84		$582.2121	$582.22	$582.25	$582.20