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	$145.76	12.808%	$164.4289	$164.43	$164.45	$164.40
Purchase #2	$113.44	8.612%	$123.2095	$123.21	$123.20	$123.20
Purchase #3	$152.50	13.263%	$172.7261	$172.73	$172.75	$172.70
Purchase #4	$89.69	12.627%	$101.0152	$101.02	$101.00	$101.00
Purchase #5	$216.80	6.174%	$230.1852	$230.19	$230.20	$230.20
Purchase #6	$69.29	3.494%	$71.711	$71.71	$71.70	$71.70
Purchase #7	$154.84	4.731%	$162.1655	$162.17	$162.15	$162.20
7 purchase totals =	$942.32		$1,025.4414	$1,025.46	$1,025.45	$1,025.40