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	$129.27	11.765%	$144.4786	$144.48	$144.50	$144.50
Purchase #2	$222.67	3.128%	$229.6351	$229.64	$229.65	$229.60
Purchase #3	$225.32	11.227%	$250.6167	$250.62	$250.60	$250.60
Purchase #4	$88.71	3.239%	$91.5833	$91.58	$91.60	$91.60
Purchase #5	$154.87	10.140%	$170.5738	$170.57	$170.55	$170.60
Purchase #6	$41.59	3.278%	$42.9533	$42.95	$42.95	$43.00
Purchase #7	$199.26	6.630%	$212.4709	$212.47	$212.45	$212.50
7 purchase totals =	$1,061.69		$1,142.3117	$1,142.31	$1,142.30	$1,142.40