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	$62.65	11.562%	$69.8936	$69.89	$69.90	$69.90
Purchase #2	$79.81	11.576%	$89.0488	$89.05	$89.05	$89.00
Purchase #3	$240.41	6.789%	$256.7314	$256.73	$256.75	$256.70
Purchase #4	$68.81	4.659%	$72.0159	$72.02	$72.00	$72.00
Purchase #5	$62.48	11.300%	$69.5402	$69.54	$69.55	$69.50
Purchase #6	$77.67	5.646%	$82.0552	$82.06	$82.05	$82.10
Purchase #7	$54.30	3.214%	$56.0452	$56.05	$56.05	$56.00
7 purchase totals =	$646.13		$695.3303	$695.34	$695.35	$695.20