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	$54.93	8.759%	$59.7413	$59.74	$59.75	$59.70
Purchase #2	$150.29	11.570%	$167.6786	$167.68	$167.70	$167.70
Purchase #3	$180.46	10.265%	$198.9842	$198.98	$199.00	$199.00
Purchase #4	$33.55	9.828%	$36.8473	$36.85	$36.85	$36.80
Purchase #5	$229.87	3.572%	$238.081	$238.08	$238.10	$238.10
Purchase #6	$10.32	9.265%	$11.2761	$11.28	$11.30	$11.30
Purchase #7	$105.48	8.218%	$114.1483	$114.15	$114.15	$114.10
7 purchase totals =	$764.90		$826.7568	$826.76	$826.85	$826.70