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	$228.55	10.829%	$253.2997	$253.30	$253.30	$253.30
Purchase #2	$240.70	13.543%	$273.298	$273.30	$273.30	$273.30
Purchase #3	$117.58	4.804%	$123.2285	$123.23	$123.25	$123.20
Purchase #4	$60.59	8.455%	$65.7129	$65.71	$65.70	$65.70
Purchase #5	$156.60	5.572%	$165.3258	$165.33	$165.35	$165.30
Purchase #6	$119.88	13.786%	$136.4067	$136.41	$136.40	$136.40
Purchase #7	$147.38	10.552%	$162.9315	$162.93	$162.95	$162.90
7 purchase totals =	$1,071.28		$1,180.2031	$1,180.21	$1,180.25	$1,180.10