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	$233.84	12.292%	$262.5836	$262.58	$262.60	$262.60
Purchase #2	$231.48	13.488%	$262.702	$262.70	$262.70	$262.70
Purchase #3	$85.93	4.374%	$89.6886	$89.69	$89.70	$89.70
Purchase #4	$109.78	12.322%	$123.3071	$123.31	$123.30	$123.30
Purchase #5	$37.50	13.587%	$42.5951	$42.60	$42.60	$42.60
Purchase #6	$91.44	8.632%	$99.3331	$99.33	$99.35	$99.30
Purchase #7	$211.25	6.762%	$225.5347	$225.53	$225.55	$225.50
7 purchase totals =	$1,001.22		$1,105.7442	$1,105.74	$1,105.80	$1,105.70