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	$216.27	7.681%	$232.8817	$232.88	$232.90	$232.90
Purchase #2	$223.86	3.712%	$232.1697	$232.17	$232.15	$232.20
Purchase #3	$156.38	10.482%	$172.7718	$172.77	$172.75	$172.80
Purchase #4	$118.69	11.493%	$132.331	$132.33	$132.35	$132.30
Purchase #5	$157.40	3.143%	$162.3471	$162.35	$162.35	$162.30
Purchase #6	$31.42	6.735%	$33.5361	$33.54	$33.55	$33.50
Purchase #7	$107.54	10.811%	$119.1661	$119.17	$119.15	$119.20
7 purchase totals =	$1,011.56		$1,085.2035	$1,085.21	$1,085.20	$1,085.20