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	$153.88	3.746%	$159.6443	$159.64	$159.65	$159.60
Purchase #2	$54.67	8.661%	$59.405	$59.41	$59.40	$59.40
Purchase #3	$223.47	4.266%	$233.0032	$233.00	$233.00	$233.00
Purchase #4	$25.29	10.516%	$27.9495	$27.95	$27.95	$27.90
Purchase #5	$39.71	10.710%	$43.9629	$43.96	$43.95	$44.00
Purchase #6	$250.28	10.792%	$277.2902	$277.29	$277.30	$277.30
Purchase #7	$55.73	6.584%	$59.3993	$59.40	$59.40	$59.40
7 purchase totals =	$803.03		$860.6544	$860.65	$860.65	$860.60