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	$157.87	11.862%	$176.5965	$176.60	$176.60	$176.60
Purchase #2	$114.61	7.674%	$123.4052	$123.41	$123.40	$123.40
Purchase #3	$242.75	12.486%	$273.0598	$273.06	$273.05	$273.10
Purchase #4	$94.56	6.263%	$100.4823	$100.48	$100.50	$100.50
Purchase #5	$114.56	7.489%	$123.1394	$123.14	$123.15	$123.10
Purchase #6	$46.89	8.183%	$50.727	$50.73	$50.75	$50.70
Purchase #7	$175.96	12.492%	$197.9409	$197.94	$197.95	$197.90
7 purchase totals =	$947.20		$1,045.3511	$1,045.36	$1,045.40	$1,045.30