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	$138.33	9.585%	$151.5889	$151.59	$151.60	$151.60
Purchase #2	$10.50	10.440%	$11.5962	$11.60	$11.60	$11.60
Purchase #3	$90.72	12.334%	$101.9094	$101.91	$101.90	$101.90
Purchase #4	$59.93	9.516%	$65.6329	$65.63	$65.65	$65.60
Purchase #5	$221.48	7.790%	$238.7333	$238.73	$238.75	$238.70
Purchase #6	$215.45	10.555%	$238.1907	$238.19	$238.20	$238.20
Purchase #7	$128.33	11.673%	$143.31	$143.31	$143.30	$143.30
7 purchase totals =	$864.74		$950.9614	$950.96	$951.00	$950.90