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	$219.41	8.843%	$238.8124	$238.81	$238.80	$238.80
Purchase #2	$136.89	9.823%	$150.3367	$150.34	$150.35	$150.30
Purchase #3	$133.69	6.784%	$142.7595	$142.76	$142.75	$142.80
Purchase #4	$59.61	8.361%	$64.594	$64.59	$64.60	$64.60
Purchase #5	$230.38	8.670%	$250.3539	$250.35	$250.35	$250.40
Purchase #6	$249.32	10.545%	$275.6108	$275.61	$275.60	$275.60
Purchase #7	$138.35	5.448%	$145.8873	$145.89	$145.90	$145.90
7 purchase totals =	$1,167.65		$1,268.3546	$1,268.35	$1,268.35	$1,268.40