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	$200.30	13.411%	$227.1622	$227.16	$227.15	$227.20
Purchase #2	$162.77	13.739%	$185.133	$185.13	$185.15	$185.10
Purchase #3	$169.27	7.751%	$182.3901	$182.39	$182.40	$182.40
Purchase #4	$28.28	11.522%	$31.5384	$31.54	$31.55	$31.50
Purchase #5	$110.47	11.869%	$123.5817	$123.58	$123.60	$123.60
Purchase #6	$108.95	5.312%	$114.7374	$114.74	$114.75	$114.70
Purchase #7	$232.30	7.416%	$249.5274	$249.53	$249.55	$249.50
7 purchase totals =	$1,012.34		$1,114.0702	$1,114.07	$1,114.15	$1,114.00