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	$88.39	4.652%	$92.5019	$92.50	$92.50	$92.50
Purchase #2	$174.94	6.234%	$185.8458	$185.85	$185.85	$185.80
Purchase #3	$151.59	6.512%	$161.4615	$161.46	$161.45	$161.50
Purchase #4	$64.72	6.303%	$68.7993	$68.80	$68.80	$68.80
Purchase #5	$17.85	6.227%	$18.9615	$18.96	$18.95	$19.00
Purchase #6	$230.58	3.440%	$238.512	$238.51	$238.50	$238.50
Purchase #7	$25.93	11.118%	$28.8129	$28.81	$28.80	$28.80
7 purchase totals =	$754.00		$794.8949	$794.89	$794.85	$794.90