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	$203.43	3.780%	$211.1197	$211.12	$211.10	$211.10
Purchase #2	$105.76	5.221%	$111.2817	$111.28	$111.30	$111.30
Purchase #3	$81.28	6.158%	$86.2852	$86.29	$86.30	$86.30
Purchase #4	$109.39	7.383%	$117.4663	$117.47	$117.45	$117.50
Purchase #5	$91.76	3.717%	$95.1707	$95.17	$95.15	$95.20
Purchase #6	$12.45	3.564%	$12.8937	$12.89	$12.90	$12.90
Purchase #7	$112.78	9.415%	$123.3982	$123.40	$123.40	$123.40
7 purchase totals =	$716.85		$757.6155	$757.62	$757.60	$757.70