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	$195.55	5.735%	$206.7648	$206.76	$206.75	$206.80
Purchase #2	$35.45	6.754%	$37.8443	$37.84	$37.85	$37.80
Purchase #3	$97.73	13.455%	$110.8796	$110.88	$110.90	$110.90
Purchase #4	$243.76	4.298%	$254.2368	$254.24	$254.25	$254.20
Purchase #5	$219.33	3.799%	$227.6623	$227.66	$227.65	$227.70
Purchase #6	$203.43	4.111%	$211.793	$211.79	$211.80	$211.80
Purchase #7	$123.32	6.567%	$131.4184	$131.42	$131.40	$131.40
7 purchase totals =	$1,118.57		$1,180.5992	$1,180.59	$1,180.60	$1,180.60