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	$58.78	7.763%	$63.3431	$63.34	$63.35	$63.30
Purchase #2	$111.59	4.577%	$116.6975	$116.70	$116.70	$116.70
Purchase #3	$99.90	10.571%	$110.4604	$110.46	$110.45	$110.50
Purchase #4	$162.41	13.849%	$184.9022	$184.90	$184.90	$184.90
Purchase #5	$159.63	5.136%	$167.8286	$167.83	$167.85	$167.80
Purchase #6	$90.72	12.186%	$101.7751	$101.78	$101.80	$101.80
Purchase #7	$115.34	6.842%	$123.2316	$123.23	$123.25	$123.20
7 purchase totals =	$798.37		$868.2385	$868.24	$868.30	$868.20