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	$116.61	5.482%	$123.0026	$123.00	$123.00	$123.00
Purchase #2	$154.84	7.514%	$166.4747	$166.47	$166.45	$166.50
Purchase #3	$38.84	7.257%	$41.6586	$41.66	$41.65	$41.70
Purchase #4	$133.79	7.714%	$144.1106	$144.11	$144.10	$144.10
Purchase #5	$196.96	10.689%	$218.0131	$218.01	$218.00	$218.00
Purchase #6	$165.25	4.830%	$173.2316	$173.23	$173.25	$173.20
Purchase #7	$59.39	3.580%	$61.5162	$61.52	$61.50	$61.50
7 purchase totals =	$865.68		$928.0074	$928.00	$927.95	$928.00