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	$128.31	11.148%	$142.614	$142.61	$142.60	$142.60
Purchase #2	$43.93	6.835%	$46.9326	$46.93	$46.95	$46.90
Purchase #3	$233.48	4.252%	$243.4076	$243.41	$243.40	$243.40
Purchase #4	$125.27	10.802%	$138.8017	$138.80	$138.80	$138.80
Purchase #5	$184.32	6.369%	$196.0593	$196.06	$196.05	$196.10
Purchase #6	$186.67	10.262%	$205.8261	$205.83	$205.85	$205.80
Purchase #7	$45.31	3.515%	$46.9026	$46.90	$46.90	$46.90
7 purchase totals =	$947.29		$1,020.5439	$1,020.54	$1,020.55	$1,020.50