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	$168.38	4.375%	$175.7466	$175.75	$175.75	$175.70
Purchase #2	$250.85	4.746%	$262.7553	$262.76	$262.75	$262.80
Purchase #3	$37.29	3.719%	$38.6768	$38.68	$38.70	$38.70
Purchase #4	$52.82	7.214%	$56.6304	$56.63	$56.65	$56.60
Purchase #5	$33.90	3.600%	$35.1204	$35.12	$35.10	$35.10
Purchase #6	$80.98	5.632%	$85.5408	$85.54	$85.55	$85.50
Purchase #7	$144.37	12.278%	$162.0957	$162.10	$162.10	$162.10
7 purchase totals =	$768.59		$816.5660	$816.58	$816.60	$816.50