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	$129.45	3.428%	$133.8875	$133.89	$133.90	$133.90
Purchase #2	$213.67	9.454%	$233.8704	$233.87	$233.85	$233.90
Purchase #3	$82.67	3.763%	$85.7809	$85.78	$85.80	$85.80
Purchase #4	$247.69	13.434%	$280.9647	$280.96	$280.95	$281.00
Purchase #5	$207.31	9.188%	$226.3576	$226.36	$226.35	$226.40
Purchase #6	$168.83	3.508%	$174.7526	$174.75	$174.75	$174.80
Purchase #7	$78.62	13.308%	$89.0827	$89.08	$89.10	$89.10
7 purchase totals =	$1,128.24		$1,224.6964	$1,224.69	$1,224.70	$1,224.90