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	$114.58	6.262%	$121.755	$121.76	$121.75	$121.80
Purchase #2	$200.50	6.650%	$213.8333	$213.83	$213.85	$213.80
Purchase #3	$94.33	11.798%	$105.4591	$105.46	$105.45	$105.50
Purchase #4	$112.36	9.437%	$122.9634	$122.96	$122.95	$123.00
Purchase #5	$106.56	13.426%	$120.8667	$120.87	$120.85	$120.90
Purchase #6	$204.72	13.276%	$231.8986	$231.90	$231.90	$231.90
Purchase #7	$219.39	6.308%	$233.2291	$233.23	$233.25	$233.20
7 purchase totals =	$1,052.44		$1,150.0052	$1,150.01	$1,150.00	$1,150.10