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	$122.89	9.259%	$134.2684	$134.27	$134.25	$134.30
Purchase #2	$111.93	6.546%	$119.2569	$119.26	$119.25	$119.30
Purchase #3	$222.37	11.860%	$248.7431	$248.74	$248.75	$248.70
Purchase #4	$147.30	12.257%	$165.3546	$165.35	$165.35	$165.40
Purchase #5	$198.63	13.723%	$225.888	$225.89	$225.90	$225.90
Purchase #6	$171.84	7.659%	$185.0012	$185.00	$185.00	$185.00
Purchase #7	$144.90	11.814%	$162.0185	$162.02	$162.00	$162.00
7 purchase totals =	$1,119.86		$1,240.5307	$1,240.53	$1,240.50	$1,240.60