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	$129.47	8.248%	$140.1487	$140.15	$140.15	$140.10
Purchase #2	$73.57	8.188%	$79.5939	$79.59	$79.60	$79.60
Purchase #3	$90.60	8.467%	$98.2711	$98.27	$98.25	$98.30
Purchase #4	$116.87	11.551%	$130.3697	$130.37	$130.35	$130.40
Purchase #5	$187.51	10.145%	$206.5329	$206.53	$206.55	$206.50
Purchase #6	$101.89	7.280%	$109.3076	$109.31	$109.30	$109.30
Purchase #7	$100.97	11.169%	$112.2473	$112.25	$112.25	$112.20
7 purchase totals =	$800.88		$876.4712	$876.47	$876.45	$876.40