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	$155.93	5.815%	$164.9973	$165.00	$165.00	$165.00
Purchase #2	$92.98	3.501%	$96.2352	$96.24	$96.25	$96.20
Purchase #3	$176.83	9.576%	$193.7632	$193.76	$193.75	$193.80
Purchase #4	$176.64	3.215%	$182.319	$182.32	$182.30	$182.30
Purchase #5	$173.31	12.127%	$194.3273	$194.33	$194.35	$194.30
Purchase #6	$86.66	4.143%	$90.2503	$90.25	$90.25	$90.30
Purchase #7	$54.40	8.716%	$59.1415	$59.14	$59.15	$59.10
7 purchase totals =	$916.75		$981.0338	$981.04	$981.05	$981.00