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	$159.34	6.560%	$169.7927	$169.79	$169.80	$169.80
Purchase #2	$101.40	3.218%	$104.6631	$104.66	$104.65	$104.70
Purchase #3	$125.64	8.188%	$135.9274	$135.93	$135.95	$135.90
Purchase #4	$150.74	12.404%	$169.4378	$169.44	$169.45	$169.40
Purchase #5	$147.66	4.611%	$154.4686	$154.47	$154.45	$154.50
Purchase #6	$81.50	11.497%	$90.8701	$90.87	$90.85	$90.90
Purchase #7	$121.38	5.258%	$127.7622	$127.76	$127.75	$127.80
7 purchase totals =	$887.66		$952.9219	$952.92	$952.90	$953.00