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	$59.60	5.753%	$63.0288	$63.03	$63.05	$63.00
Purchase #2	$71.70	12.146%	$80.4087	$80.41	$80.40	$80.40
Purchase #3	$196.27	4.682%	$205.4594	$205.46	$205.45	$205.50
Purchase #4	$72.58	11.626%	$81.0182	$81.02	$81.00	$81.00
Purchase #5	$61.29	10.412%	$67.6715	$67.67	$67.65	$67.70
Purchase #6	$223.77	6.590%	$238.5164	$238.52	$238.50	$238.50
Purchase #7	$46.27	3.643%	$47.9556	$47.96	$47.95	$48.00
7 purchase totals =	$731.48		$784.0586	$784.07	$784.00	$784.10