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	$207.51	5.275%	$218.4562	$218.46	$218.45	$218.50
Purchase #2	$209.96	7.782%	$226.2991	$226.30	$226.30	$226.30
Purchase #3	$148.82	9.237%	$162.5665	$162.57	$162.55	$162.60
Purchase #4	$66.86	7.150%	$71.6405	$71.64	$71.65	$71.60
Purchase #5	$32.89	12.667%	$37.0562	$37.06	$37.05	$37.10
Purchase #6	$24.29	13.623%	$27.599	$27.60	$27.60	$27.60
Purchase #7	$54.59	6.244%	$57.9986	$58.00	$58.00	$58.00
7 purchase totals =	$744.92		$801.6161	$801.63	$801.60	$801.70