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	$225.73	5.576%	$238.3167	$238.32	$238.30	$238.30
Purchase #2	$241.29	10.185%	$265.8654	$265.87	$265.85	$265.90
Purchase #3	$168.53	9.490%	$184.5235	$184.52	$184.50	$184.50
Purchase #4	$26.66	5.217%	$28.0509	$28.05	$28.05	$28.10
Purchase #5	$63.93	13.608%	$72.6296	$72.63	$72.65	$72.60
Purchase #6	$97.59	7.480%	$104.8897	$104.89	$104.90	$104.90
Purchase #7	$118.36	4.543%	$123.7371	$123.74	$123.75	$123.70
7 purchase totals =	$942.09		$1,018.0129	$1,018.02	$1,018.00	$1,018.00