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	$233.69	8.445%	$253.4251	$253.43	$253.45	$253.40
Purchase #2	$210.78	12.322%	$236.7523	$236.75	$236.75	$236.80
Purchase #3	$54.45	9.160%	$59.4376	$59.44	$59.45	$59.40
Purchase #4	$163.52	13.802%	$186.089	$186.09	$186.10	$186.10
Purchase #5	$39.87	4.645%	$41.722	$41.72	$41.70	$41.70
Purchase #6	$90.59	9.745%	$99.418	$99.42	$99.40	$99.40
Purchase #7	$121.81	9.867%	$133.829	$133.83	$133.85	$133.80
7 purchase totals =	$914.71		$1,010.6730	$1,010.68	$1,010.70	$1,010.60