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	$209.31	3.811%	$217.2868	$217.29	$217.30	$217.30
Purchase #2	$179.55	4.844%	$188.2474	$188.25	$188.25	$188.20
Purchase #3	$159.88	9.754%	$175.4747	$175.47	$175.45	$175.50
Purchase #4	$67.34	9.227%	$73.5535	$73.55	$73.55	$73.60
Purchase #5	$27.48	11.314%	$30.5891	$30.59	$30.60	$30.60
Purchase #6	$189.38	3.835%	$196.6427	$196.64	$196.65	$196.60
Purchase #7	$201.64	8.533%	$218.8459	$218.85	$218.85	$218.80
7 purchase totals =	$1,034.58		$1,100.6401	$1,100.64	$1,100.65	$1,100.60