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	$194.41	9.614%	$213.1006	$213.10	$213.10	$213.10
Purchase #2	$219.72	3.734%	$227.9243	$227.92	$227.90	$227.90
Purchase #3	$40.29	5.849%	$42.6466	$42.65	$42.65	$42.60
Purchase #4	$100.67	8.480%	$109.2068	$109.21	$109.20	$109.20
Purchase #5	$183.65	7.259%	$196.9812	$196.98	$197.00	$197.00
Purchase #6	$101.41	9.489%	$111.0328	$111.03	$111.05	$111.00
Purchase #7	$225.34	7.557%	$242.3689	$242.37	$242.35	$242.40
7 purchase totals =	$1,065.49		$1,143.2612	$1,143.26	$1,143.25	$1,143.20