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	$163.93	11.764%	$183.2147	$183.21	$183.20	$183.20
Purchase #2	$140.34	7.129%	$150.3448	$150.34	$150.35	$150.30
Purchase #3	$156.38	3.151%	$161.3075	$161.31	$161.30	$161.30
Purchase #4	$195.48	11.603%	$218.1615	$218.16	$218.15	$218.20
Purchase #5	$99.56	4.144%	$103.6858	$103.69	$103.70	$103.70
Purchase #6	$19.74	7.111%	$21.1437	$21.14	$21.15	$21.10
Purchase #7	$112.29	13.186%	$127.0966	$127.10	$127.10	$127.10
7 purchase totals =	$887.72		$964.9546	$964.95	$964.95	$964.90