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	$56.42	4.837%	$59.149	$59.15	$59.15	$59.10
Purchase #2	$241.62	3.172%	$249.2842	$249.28	$249.30	$249.30
Purchase #3	$96.77	12.355%	$108.7259	$108.73	$108.75	$108.70
Purchase #4	$171.43	13.835%	$195.1473	$195.15	$195.15	$195.10
Purchase #5	$7.73	6.410%	$8.2255	$8.23	$8.25	$8.20
Purchase #6	$169.71	4.215%	$176.8633	$176.86	$176.85	$176.90
Purchase #7	$132.45	13.791%	$150.7162	$150.72	$150.70	$150.70
7 purchase totals =	$876.13		$948.1114	$948.12	$948.15	$948.00