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	$201.32	13.716%	$228.9331	$228.93	$228.95	$228.90
Purchase #2	$185.91	4.448%	$194.1793	$194.18	$194.20	$194.20
Purchase #3	$65.61	8.521%	$71.2006	$71.20	$71.20	$71.20
Purchase #4	$96.82	13.161%	$109.5625	$109.56	$109.55	$109.60
Purchase #5	$155.67	10.175%	$171.5094	$171.51	$171.50	$171.50
Purchase #6	$133.35	9.709%	$146.297	$146.30	$146.30	$146.30
Purchase #7	$83.57	7.173%	$89.5645	$89.56	$89.55	$89.60
7 purchase totals =	$922.25		$1,011.2464	$1,011.24	$1,011.25	$1,011.30