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	$93.73	11.586%	$104.5896	$104.59	$104.60	$104.60
Purchase #2	$218.94	12.145%	$245.5303	$245.53	$245.55	$245.50
Purchase #3	$182.86	8.585%	$198.5585	$198.56	$198.55	$198.60
Purchase #4	$86.81	4.222%	$90.4751	$90.48	$90.50	$90.50
Purchase #5	$148.58	4.782%	$155.6851	$155.69	$155.70	$155.70
Purchase #6	$237.48	4.448%	$248.0431	$248.04	$248.05	$248.00
Purchase #7	$94.84	12.217%	$106.4266	$106.43	$106.45	$106.40
7 purchase totals =	$1,063.24		$1,149.3083	$1,149.32	$1,149.40	$1,149.30