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	$223.55	10.661%	$247.3827	$247.38	$247.40	$247.40
Purchase #2	$210.68	10.638%	$233.0921	$233.09	$233.10	$233.10
Purchase #3	$42.46	11.438%	$47.3166	$47.32	$47.30	$47.30
Purchase #4	$119.33	10.333%	$131.6604	$131.66	$131.65	$131.70
Purchase #5	$72.85	7.536%	$78.34	$78.34	$78.35	$78.30
Purchase #6	$246.66	8.809%	$268.3883	$268.39	$268.40	$268.40
Purchase #7	$139.36	8.314%	$150.9464	$150.95	$150.95	$150.90
7 purchase totals =	$1,054.89		$1,157.1265	$1,157.13	$1,157.15	$1,157.10