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	$53.72	5.435%	$56.6397	$56.64	$56.65	$56.60
Purchase #2	$189.59	4.679%	$198.4609	$198.46	$198.45	$198.50
Purchase #3	$119.77	8.807%	$130.3181	$130.32	$130.30	$130.30
Purchase #4	$58.58	4.102%	$60.983	$60.98	$61.00	$61.00
Purchase #5	$148.77	12.450%	$167.2919	$167.29	$167.30	$167.30
Purchase #6	$74.69	10.596%	$82.6042	$82.60	$82.60	$82.60
Purchase #7	$47.68	8.265%	$51.6208	$51.62	$51.60	$51.60
7 purchase totals =	$692.80		$747.9186	$747.91	$747.90	$747.90