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	$121.74	10.421%	$134.4265	$134.43	$134.45	$134.40
Purchase #2	$201.53	13.860%	$229.4621	$229.46	$229.45	$229.50
Purchase #3	$87.97	4.697%	$92.102	$92.10	$92.10	$92.10
Purchase #4	$240.58	11.642%	$268.5883	$268.59	$268.60	$268.60
Purchase #5	$122.30	9.801%	$134.2866	$134.29	$134.30	$134.30
Purchase #6	$90.38	10.370%	$99.7524	$99.75	$99.75	$99.80
Purchase #7	$145.54	5.167%	$153.0601	$153.06	$153.05	$153.10
7 purchase totals =	$1,010.04		$1,111.6780	$1,111.68	$1,111.70	$1,111.80