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	$232.55	5.501%	$245.3426	$245.34	$245.35	$245.30
Purchase #2	$81.59	12.716%	$91.965	$91.97	$91.95	$92.00
Purchase #3	$200.44	13.833%	$228.1669	$228.17	$228.15	$228.20
Purchase #4	$79.78	6.593%	$85.0399	$85.04	$85.05	$85.00
Purchase #5	$66.83	11.728%	$74.6678	$74.67	$74.65	$74.70
Purchase #6	$228.43	4.342%	$238.3484	$238.35	$238.35	$238.30
Purchase #7	$80.88	11.433%	$90.127	$90.13	$90.15	$90.10
7 purchase totals =	$970.50		$1,053.6576	$1,053.67	$1,053.65	$1,053.60