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	$232.75	5.650%	$245.9004	$245.90	$245.90	$245.90
Purchase #2	$5.31	10.483%	$5.8666	$5.87	$5.85	$5.90
Purchase #3	$86.72	3.465%	$89.7248	$89.72	$89.70	$89.70
Purchase #4	$199.33	10.391%	$220.0424	$220.04	$220.05	$220.00
Purchase #5	$100.92	8.573%	$109.5719	$109.57	$109.55	$109.60
Purchase #6	$40.94	8.855%	$44.5652	$44.57	$44.55	$44.60
Purchase #7	$136.27	4.580%	$142.5112	$142.51	$142.50	$142.50
7 purchase totals =	$802.24		$858.1825	$858.18	$858.10	$858.20