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	$62.41	13.812%	$71.0301	$71.03	$71.05	$71.00
Purchase #2	$91.85	9.260%	$100.3553	$100.36	$100.35	$100.40
Purchase #3	$49.82	12.659%	$56.1267	$56.13	$56.15	$56.10
Purchase #4	$190.61	7.527%	$204.9572	$204.96	$204.95	$205.00
Purchase #5	$69.42	9.498%	$76.0135	$76.01	$76.00	$76.00
Purchase #6	$169.44	12.786%	$191.1046	$191.10	$191.10	$191.10
Purchase #7	$124.72	3.363%	$128.9143	$128.91	$128.90	$128.90
7 purchase totals =	$758.27		$828.5017	$828.50	$828.50	$828.50