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	$187.33	3.672%	$194.2088	$194.21	$194.20	$194.20
Purchase #2	$55.86	9.851%	$61.3628	$61.36	$61.35	$61.40
Purchase #3	$155.50	11.454%	$173.311	$173.31	$173.30	$173.30
Purchase #4	$57.59	3.833%	$59.7974	$59.80	$59.80	$59.80
Purchase #5	$246.44	6.653%	$262.8357	$262.84	$262.85	$262.80
Purchase #6	$42.66	7.338%	$45.7904	$45.79	$45.80	$45.80
Purchase #7	$112.83	5.305%	$118.8156	$118.82	$118.80	$118.80
7 purchase totals =	$858.21		$916.1217	$916.13	$916.10	$916.10