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	$151.47	3.170%	$156.2716	$156.27	$156.25	$156.30
Purchase #2	$90.73	8.223%	$98.1907	$98.19	$98.20	$98.20
Purchase #3	$130.87	8.740%	$142.308	$142.31	$142.30	$142.30
Purchase #4	$175.37	3.655%	$181.7798	$181.78	$181.80	$181.80
Purchase #5	$210.82	4.407%	$220.1108	$220.11	$220.10	$220.10
Purchase #6	$190.73	3.598%	$197.5925	$197.59	$197.60	$197.60
Purchase #7	$134.31	12.247%	$150.7589	$150.76	$150.75	$150.80
7 purchase totals =	$1,084.30		$1,147.0123	$1,147.01	$1,147.00	$1,147.10