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	$223.78	11.797%	$250.1793	$250.18	$250.20	$250.20
Purchase #2	$73.57	10.690%	$81.4346	$81.43	$81.45	$81.40
Purchase #3	$250.59	9.444%	$274.2557	$274.26	$274.25	$274.30
Purchase #4	$196.94	10.306%	$217.2366	$217.24	$217.25	$217.20
Purchase #5	$90.79	9.329%	$99.2598	$99.26	$99.25	$99.30
Purchase #6	$104.32	10.114%	$114.8709	$114.87	$114.85	$114.90
Purchase #7	$48.76	11.483%	$54.3591	$54.36	$54.35	$54.40
7 purchase totals =	$988.75		$1,091.5960	$1,091.60	$1,091.60	$1,091.70