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	$141.31	10.686%	$156.4104	$156.41	$156.40	$156.40
Purchase #2	$247.59	5.744%	$261.8116	$261.81	$261.80	$261.80
Purchase #3	$59.33	13.251%	$67.1918	$67.19	$67.20	$67.20
Purchase #4	$73.77	13.331%	$83.6043	$83.60	$83.60	$83.60
Purchase #5	$187.82	11.337%	$209.1132	$209.11	$209.10	$209.10
Purchase #6	$226.51	8.812%	$246.4701	$246.47	$246.45	$246.50
Purchase #7	$19.92	8.151%	$21.5437	$21.54	$21.55	$21.50
7 purchase totals =	$956.25		$1,046.1451	$1,046.13	$1,046.10	$1,046.10