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	$164.30	5.812%	$173.8491	$173.85	$173.85	$173.80
Purchase #2	$116.25	10.535%	$128.4969	$128.50	$128.50	$128.50
Purchase #3	$145.76	6.645%	$155.4458	$155.45	$155.45	$155.40
Purchase #4	$98.27	11.466%	$109.5376	$109.54	$109.55	$109.50
Purchase #5	$250.60	9.807%	$275.1763	$275.18	$275.20	$275.20
Purchase #6	$183.73	13.454%	$208.449	$208.45	$208.45	$208.40
Purchase #7	$163.53	10.446%	$180.6123	$180.61	$180.60	$180.60
7 purchase totals =	$1,122.44		$1,231.5670	$1,231.58	$1,231.60	$1,231.40