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	$62.92	7.325%	$67.5289	$67.53	$67.55	$67.50
Purchase #2	$93.55	6.311%	$99.4539	$99.45	$99.45	$99.50
Purchase #3	$189.33	5.456%	$199.6598	$199.66	$199.65	$199.70
Purchase #4	$180.63	10.364%	$199.3505	$199.35	$199.35	$199.40
Purchase #5	$142.92	12.382%	$160.6164	$160.62	$160.60	$160.60
Purchase #6	$72.89	11.524%	$81.2898	$81.29	$81.30	$81.30
Purchase #7	$174.63	9.658%	$191.4958	$191.50	$191.50	$191.50
7 purchase totals =	$916.87		$999.3951	$999.40	$999.40	$999.50