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	$63.56	6.870%	$67.9266	$67.93	$67.95	$67.90
Purchase #2	$216.62	8.843%	$235.7757	$235.78	$235.80	$235.80
Purchase #3	$59.43	4.355%	$62.0182	$62.02	$62.00	$62.00
Purchase #4	$147.51	10.123%	$162.4424	$162.44	$162.45	$162.40
Purchase #5	$214.85	13.256%	$243.3305	$243.33	$243.35	$243.30
Purchase #6	$99.35	6.175%	$105.4849	$105.48	$105.50	$105.50
Purchase #7	$122.98	4.111%	$128.0357	$128.04	$128.05	$128.00
7 purchase totals =	$924.30		$1,005.0140	$1,005.02	$1,005.10	$1,004.90