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	$153.88	10.586%	$170.1697	$170.17	$170.15	$170.20
Purchase #2	$99.30	10.129%	$109.3581	$109.36	$109.35	$109.40
Purchase #3	$143.56	10.670%	$158.8779	$158.88	$158.90	$158.90
Purchase #4	$5.64	9.312%	$6.1652	$6.17	$6.15	$6.20
Purchase #5	$98.48	5.268%	$103.6679	$103.67	$103.65	$103.70
Purchase #6	$131.88	10.627%	$145.8949	$145.89	$145.90	$145.90
Purchase #7	$159.57	13.625%	$181.3114	$181.31	$181.30	$181.30
7 purchase totals =	$792.31		$875.4451	$875.45	$875.40	$875.60