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	$141.92	10.639%	$157.0189	$157.02	$157.00	$157.00
Purchase #2	$13.88	10.540%	$15.343	$15.34	$15.35	$15.30
Purchase #3	$81.30	3.395%	$84.0601	$84.06	$84.05	$84.10
Purchase #4	$185.86	5.713%	$196.4782	$196.48	$196.50	$196.50
Purchase #5	$130.87	11.383%	$145.7669	$145.77	$145.75	$145.80
Purchase #6	$206.54	8.363%	$223.8129	$223.81	$223.80	$223.80
Purchase #7	$52.36	3.806%	$54.3528	$54.35	$54.35	$54.40
7 purchase totals =	$812.73		$876.8328	$876.83	$876.80	$876.90