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	$32.76	13.404%	$37.1512	$37.15	$37.15	$37.20
Purchase #2	$178.61	3.271%	$184.4523	$184.45	$184.45	$184.50
Purchase #3	$225.38	7.513%	$242.3128	$242.31	$242.30	$242.30
Purchase #4	$80.58	11.784%	$90.0755	$90.08	$90.10	$90.10
Purchase #5	$173.94	4.795%	$182.2804	$182.28	$182.30	$182.30
Purchase #6	$114.66	11.547%	$127.8998	$127.90	$127.90	$127.90
Purchase #7	$200.42	4.446%	$209.3307	$209.33	$209.35	$209.30
7 purchase totals =	$1,006.35		$1,073.5027	$1,073.50	$1,073.55	$1,073.60