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	$65.40	11.524%	$72.9367	$72.94	$72.95	$72.90
Purchase #2	$101.78	11.296%	$113.2771	$113.28	$113.30	$113.30
Purchase #3	$173.92	4.193%	$181.2125	$181.21	$181.20	$181.20
Purchase #4	$37.54	3.418%	$38.8231	$38.82	$38.80	$38.80
Purchase #5	$147.90	11.702%	$165.2073	$165.21	$165.20	$165.20
Purchase #6	$191.89	11.470%	$213.8998	$213.90	$213.90	$213.90
Purchase #7	$148.39	5.445%	$156.4698	$156.47	$156.45	$156.50
7 purchase totals =	$866.82		$941.8263	$941.83	$941.80	$941.80