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	$194.61	12.789%	$219.4987	$219.50	$219.50	$219.50
Purchase #2	$113.35	9.393%	$123.997	$124.00	$124.00	$124.00
Purchase #3	$172.69	9.327%	$188.7968	$188.80	$188.80	$188.80
Purchase #4	$242.47	12.761%	$273.4116	$273.41	$273.40	$273.40
Purchase #5	$133.35	13.452%	$151.2882	$151.29	$151.30	$151.30
Purchase #6	$186.36	12.349%	$209.3736	$209.37	$209.35	$209.40
Purchase #7	$121.35	5.149%	$127.5983	$127.60	$127.60	$127.60
7 purchase totals =	$1,164.18		$1,293.9642	$1,293.97	$1,293.95	$1,294.00