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	$42.31	10.314%	$46.6739	$46.67	$46.65	$46.70
Purchase #2	$108.47	5.366%	$114.2905	$114.29	$114.30	$114.30
Purchase #3	$156.79	9.872%	$172.2683	$172.27	$172.25	$172.30
Purchase #4	$232.64	10.312%	$256.6298	$256.63	$256.65	$256.60
Purchase #5	$228.34	9.708%	$250.5072	$250.51	$250.50	$250.50
Purchase #6	$84.54	4.657%	$88.477	$88.48	$88.50	$88.50
Purchase #7	$55.47	7.189%	$59.4577	$59.46	$59.45	$59.50
7 purchase totals =	$908.56		$988.3044	$988.31	$988.30	$988.40