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	$201.72	12.596%	$227.1287	$227.13	$227.15	$227.10
Purchase #2	$73.79	6.427%	$78.5325	$78.53	$78.55	$78.50
Purchase #3	$180.69	4.308%	$188.4741	$188.47	$188.45	$188.50
Purchase #4	$188.96	8.529%	$205.0764	$205.08	$205.10	$205.10
Purchase #5	$241.96	3.758%	$251.0529	$251.05	$251.05	$251.10
Purchase #6	$69.61	12.845%	$78.5514	$78.55	$78.55	$78.60
Purchase #7	$189.72	8.808%	$206.4305	$206.43	$206.45	$206.40
7 purchase totals =	$1,146.45		$1,235.2465	$1,235.24	$1,235.30	$1,235.30