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	$25.28	9.471%	$27.6743	$27.67	$27.65	$27.70
Purchase #2	$94.46	4.471%	$98.6833	$98.68	$98.70	$98.70
Purchase #3	$135.73	12.538%	$152.7478	$152.75	$152.75	$152.70
Purchase #4	$96.82	4.185%	$100.8719	$100.87	$100.85	$100.90
Purchase #5	$249.74	13.663%	$283.862	$283.86	$283.85	$283.90
Purchase #6	$60.34	8.722%	$65.6029	$65.60	$65.60	$65.60
Purchase #7	$150.47	6.252%	$159.8774	$159.88	$159.90	$159.90
7 purchase totals =	$812.84		$889.3196	$889.31	$889.30	$889.40