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	$186.39	5.287%	$196.2444	$196.24	$196.25	$196.20
Purchase #2	$167.57	7.648%	$180.3858	$180.39	$180.40	$180.40
Purchase #3	$219.63	11.195%	$244.2176	$244.22	$244.20	$244.20
Purchase #4	$148.91	5.292%	$156.7903	$156.79	$156.80	$156.80
Purchase #5	$183.62	6.778%	$196.0658	$196.07	$196.05	$196.10
Purchase #6	$78.49	11.595%	$87.5909	$87.59	$87.60	$87.60
Purchase #7	$150.35	11.176%	$167.1531	$167.15	$167.15	$167.20
7 purchase totals =	$1,134.96		$1,228.4479	$1,228.45	$1,228.45	$1,228.50