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	$118.97	7.219%	$127.5584	$127.56	$127.55	$127.60
Purchase #2	$20.79	13.743%	$23.6472	$23.65	$23.65	$23.60
Purchase #3	$152.82	12.840%	$172.4421	$172.44	$172.45	$172.40
Purchase #4	$53.51	8.654%	$58.1408	$58.14	$58.15	$58.10
Purchase #5	$71.94	11.629%	$80.3059	$80.31	$80.30	$80.30
Purchase #6	$162.25	3.335%	$167.661	$167.66	$167.65	$167.70
Purchase #7	$143.99	4.258%	$150.1211	$150.12	$150.10	$150.10
7 purchase totals =	$724.27		$779.8765	$779.88	$779.85	$779.80