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	$205.31	5.650%	$216.91	$216.91	$216.90	$216.90
Purchase #2	$84.73	13.596%	$96.2499	$96.25	$96.25	$96.20
Purchase #3	$42.39	7.508%	$45.5726	$45.57	$45.55	$45.60
Purchase #4	$38.52	11.355%	$42.8939	$42.89	$42.90	$42.90
Purchase #5	$50.83	4.565%	$53.1504	$53.15	$53.15	$53.20
Purchase #6	$115.37	3.506%	$119.4149	$119.41	$119.40	$119.40
Purchase #7	$37.91	10.643%	$41.9448	$41.94	$41.95	$41.90
7 purchase totals =	$575.06		$616.1365	$616.12	$616.10	$616.10