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	$150.36	10.140%	$165.6065	$165.61	$165.60	$165.60
Purchase #2	$50.41	11.422%	$56.1678	$56.17	$56.15	$56.20
Purchase #3	$240.59	11.552%	$268.383	$268.38	$268.40	$268.40
Purchase #4	$229.98	8.524%	$249.5835	$249.58	$249.60	$249.60
Purchase #5	$147.28	6.874%	$157.404	$157.40	$157.40	$157.40
Purchase #6	$18.85	3.264%	$19.4653	$19.47	$19.45	$19.50
Purchase #7	$85.89	7.504%	$92.3352	$92.34	$92.35	$92.30
7 purchase totals =	$923.36		$1,008.9453	$1,008.95	$1,008.95	$1,009.00