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	$128.54	3.734%	$133.3397	$133.34	$133.35	$133.30
Purchase #2	$208.48	9.802%	$228.9152	$228.92	$228.90	$228.90
Purchase #3	$36.42	6.605%	$38.8255	$38.83	$38.85	$38.80
Purchase #4	$31.46	6.754%	$33.5848	$33.58	$33.60	$33.60
Purchase #5	$179.75	13.666%	$204.3146	$204.31	$204.30	$204.30
Purchase #6	$35.82	5.661%	$37.8478	$37.85	$37.85	$37.80
Purchase #7	$73.47	6.554%	$78.2852	$78.29	$78.30	$78.30
7 purchase totals =	$693.94		$755.1128	$755.12	$755.15	$755.00