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	$48.35	11.140%	$53.7362	$53.74	$53.75	$53.70
Purchase #2	$105.36	10.384%	$116.3006	$116.30	$116.30	$116.30
Purchase #3	$198.39	12.348%	$222.8872	$222.89	$222.90	$222.90
Purchase #4	$130.51	7.258%	$139.9824	$139.98	$140.00	$140.00
Purchase #5	$232.92	4.625%	$243.6926	$243.69	$243.70	$243.70
Purchase #6	$71.56	8.337%	$77.526	$77.53	$77.55	$77.50
Purchase #7	$6.85	8.165%	$7.4093	$7.41	$7.40	$7.40
7 purchase totals =	$793.94		$861.5343	$861.54	$861.60	$861.50