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	$99.54	12.598%	$112.08	$112.08	$112.10	$112.10
Purchase #2	$215.86	13.541%	$245.0896	$245.09	$245.10	$245.10
Purchase #3	$49.95	8.800%	$54.3456	$54.35	$54.35	$54.30
Purchase #4	$64.94	12.865%	$73.2945	$73.29	$73.30	$73.30
Purchase #5	$152.79	12.609%	$172.0553	$172.06	$172.05	$172.10
Purchase #6	$53.61	10.207%	$59.082	$59.08	$59.10	$59.10
Purchase #7	$14.68	7.411%	$15.7679	$15.77	$15.75	$15.80
7 purchase totals =	$651.37		$731.7149	$731.72	$731.75	$731.80