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	$83.84	7.767%	$90.3519	$90.35	$90.35	$90.40
Purchase #2	$89.76	13.790%	$102.1379	$102.14	$102.15	$102.10
Purchase #3	$9.45	10.732%	$10.4642	$10.46	$10.45	$10.50
Purchase #4	$46.27	5.768%	$48.9389	$48.94	$48.95	$48.90
Purchase #5	$93.36	6.334%	$99.2734	$99.27	$99.25	$99.30
Purchase #6	$43.57	8.663%	$47.3445	$47.34	$47.35	$47.30
Purchase #7	$9.28	9.694%	$10.1796	$10.18	$10.20	$10.20
7 purchase totals =	$375.53		$408.6904	$408.68	$408.70	$408.70