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	$70.82	3.505%	$73.3022	$73.30	$73.30	$73.30
Purchase #2	$136.37	11.829%	$152.5012	$152.50	$152.50	$152.50
Purchase #3	$172.39	12.311%	$193.6129	$193.61	$193.60	$193.60
Purchase #4	$226.83	3.612%	$235.0231	$235.02	$235.00	$235.00
Purchase #5	$56.59	10.482%	$62.5218	$62.52	$62.50	$62.50
Purchase #6	$171.59	8.784%	$186.6625	$186.66	$186.65	$186.70
Purchase #7	$95.73	9.520%	$104.8435	$104.84	$104.85	$104.80
7 purchase totals =	$930.32		$1,008.4672	$1,008.45	$1,008.40	$1,008.40