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	$185.67	5.754%	$196.3535	$196.35	$196.35	$196.40
Purchase #2	$64.71	5.743%	$68.4263	$68.43	$68.45	$68.40
Purchase #3	$63.60	5.432%	$67.0548	$67.05	$67.05	$67.10
Purchase #4	$106.77	9.851%	$117.2879	$117.29	$117.30	$117.30
Purchase #5	$28.79	5.782%	$30.4546	$30.45	$30.45	$30.50
Purchase #6	$30.58	7.828%	$32.9738	$32.97	$32.95	$33.00
Purchase #7	$139.78	10.687%	$154.7183	$154.72	$154.70	$154.70
7 purchase totals =	$619.90		$667.2692	$667.26	$667.25	$667.40