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	$104.62	7.778%	$112.7573	$112.76	$112.75	$112.80
Purchase #2	$119.36	3.401%	$123.4194	$123.42	$123.40	$123.40
Purchase #3	$114.39	7.803%	$123.3159	$123.32	$123.30	$123.30
Purchase #4	$67.42	4.116%	$70.195	$70.20	$70.20	$70.20
Purchase #5	$96.47	12.850%	$108.8664	$108.87	$108.85	$108.90
Purchase #6	$178.85	10.531%	$197.6847	$197.68	$197.70	$197.70
Purchase #7	$100.53	11.700%	$112.292	$112.29	$112.30	$112.30
7 purchase totals =	$781.64		$848.5307	$848.54	$848.50	$848.60