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	$240.79	6.566%	$256.6003	$256.60	$256.60	$256.60
Purchase #2	$12.86	6.400%	$13.683	$13.68	$13.70	$13.70
Purchase #3	$162.89	6.121%	$172.8605	$172.86	$172.85	$172.90
Purchase #4	$243.64	11.120%	$270.7328	$270.73	$270.75	$270.70
Purchase #5	$106.60	12.155%	$119.5572	$119.56	$119.55	$119.60
Purchase #6	$199.84	5.446%	$210.7233	$210.72	$210.70	$210.70
Purchase #7	$142.98	6.519%	$152.3009	$152.30	$152.30	$152.30
7 purchase totals =	$1,109.60		$1,196.4580	$1,196.45	$1,196.45	$1,196.50