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	$133.37	8.225%	$144.3397	$144.34	$144.35	$144.30
Purchase #2	$170.42	11.667%	$190.3029	$190.30	$190.30	$190.30
Purchase #3	$160.38	4.822%	$168.1135	$168.11	$168.10	$168.10
Purchase #4	$160.38	11.601%	$178.9857	$178.99	$179.00	$179.00
Purchase #5	$72.62	13.680%	$82.5544	$82.55	$82.55	$82.60
Purchase #6	$214.62	6.361%	$228.272	$228.27	$228.25	$228.30
Purchase #7	$238.42	13.238%	$269.982	$269.98	$270.00	$270.00
7 purchase totals =	$1,150.21		$1,262.5502	$1,262.54	$1,262.55	$1,262.60