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	$177.42	11.681%	$198.1444	$198.14	$198.15	$198.10
Purchase #2	$42.36	7.203%	$45.4112	$45.41	$45.40	$45.40
Purchase #3	$61.60	9.683%	$67.5647	$67.56	$67.55	$67.60
Purchase #4	$171.40	11.220%	$190.6311	$190.63	$190.65	$190.60
Purchase #5	$172.91	8.441%	$187.5053	$187.51	$187.50	$187.50
Purchase #6	$98.25	11.493%	$109.5419	$109.54	$109.55	$109.50
Purchase #7	$170.65	11.260%	$189.8652	$189.87	$189.85	$189.90
7 purchase totals =	$894.59		$988.6638	$988.66	$988.65	$988.60