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	$198.46	5.636%	$209.6452	$209.65	$209.65	$209.60
Purchase #2	$82.80	6.342%	$88.0512	$88.05	$88.05	$88.10
Purchase #3	$84.48	7.686%	$90.9731	$90.97	$90.95	$91.00
Purchase #4	$89.33	10.307%	$98.5372	$98.54	$98.55	$98.50
Purchase #5	$30.36	5.686%	$32.0863	$32.09	$32.10	$32.10
Purchase #6	$227.93	12.128%	$255.5734	$255.57	$255.55	$255.60
Purchase #7	$124.90	11.840%	$139.6882	$139.69	$139.70	$139.70
7 purchase totals =	$838.26		$914.5546	$914.56	$914.55	$914.60