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	$219.61	12.774%	$247.663	$247.66	$247.65	$247.70
Purchase #2	$204.33	5.648%	$215.8706	$215.87	$215.85	$215.90
Purchase #3	$150.71	13.815%	$171.5306	$171.53	$171.55	$171.50
Purchase #4	$162.62	13.696%	$184.8924	$184.89	$184.90	$184.90
Purchase #5	$203.48	3.699%	$211.0067	$211.01	$211.00	$211.00
Purchase #6	$236.98	7.592%	$254.9715	$254.97	$254.95	$255.00
Purchase #7	$37.42	9.465%	$40.9618	$40.96	$40.95	$41.00
7 purchase totals =	$1,215.15		$1,326.8966	$1,326.89	$1,326.85	$1,327.00