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	$243.54	13.593%	$276.6444	$276.64	$276.65	$276.60
Purchase #2	$123.69	6.424%	$131.6358	$131.64	$131.65	$131.60
Purchase #3	$217.63	5.509%	$229.6192	$229.62	$229.60	$229.60
Purchase #4	$88.88	6.422%	$94.5879	$94.59	$94.60	$94.60
Purchase #5	$240.70	13.497%	$273.1873	$273.19	$273.20	$273.20
Purchase #6	$79.61	4.399%	$83.112	$83.11	$83.10	$83.10
Purchase #7	$89.66	3.232%	$92.5578	$92.56	$92.55	$92.60
7 purchase totals =	$1,083.71		$1,181.3444	$1,181.35	$1,181.35	$1,181.30