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	$119.68	5.419%	$126.1655	$126.17	$126.15	$126.20
Purchase #2	$96.38	13.387%	$109.2824	$109.28	$109.30	$109.30
Purchase #3	$249.91	11.449%	$278.5222	$278.52	$278.50	$278.50
Purchase #4	$51.51	5.848%	$54.5223	$54.52	$54.50	$54.50
Purchase #5	$131.27	3.497%	$135.8605	$135.86	$135.85	$135.90
Purchase #6	$62.63	8.197%	$67.7638	$67.76	$67.75	$67.80
Purchase #7	$101.56	3.139%	$104.748	$104.75	$104.75	$104.70
7 purchase totals =	$812.94		$876.8647	$876.86	$876.80	$876.90