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	$18.60	11.553%	$20.7489	$20.75	$20.75	$20.70
Purchase #2	$218.98	12.506%	$246.3656	$246.37	$246.35	$246.40
Purchase #3	$33.42	13.537%	$37.9441	$37.94	$37.95	$37.90
Purchase #4	$156.45	12.416%	$175.8748	$175.87	$175.85	$175.90
Purchase #5	$221.87	3.216%	$229.0053	$229.01	$229.00	$229.00
Purchase #6	$109.25	3.663%	$113.2518	$113.25	$113.25	$113.30
Purchase #7	$250.72	4.790%	$262.7295	$262.73	$262.75	$262.70
7 purchase totals =	$1,009.29		$1,085.9200	$1,085.92	$1,085.90	$1,085.90