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	$155.36	4.839%	$162.8779	$162.88	$162.90	$162.90
Purchase #2	$165.38	10.832%	$183.294	$183.29	$183.30	$183.30
Purchase #3	$11.31	10.418%	$12.4883	$12.49	$12.50	$12.50
Purchase #4	$117.25	6.178%	$124.4937	$124.49	$124.50	$124.50
Purchase #5	$166.54	3.837%	$172.9301	$172.93	$172.95	$172.90
Purchase #6	$98.33	11.157%	$109.3007	$109.30	$109.30	$109.30
Purchase #7	$189.27	4.381%	$197.5619	$197.56	$197.55	$197.60
7 purchase totals =	$903.44		$962.9466	$962.94	$963.00	$963.00