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	$214.56	3.437%	$221.9344	$221.93	$221.95	$221.90
Purchase #2	$55.54	9.540%	$60.8385	$60.84	$60.85	$60.80
Purchase #3	$29.88	6.488%	$31.8186	$31.82	$31.80	$31.80
Purchase #4	$210.67	11.170%	$234.2018	$234.20	$234.20	$234.20
Purchase #5	$48.83	9.569%	$53.5025	$53.50	$53.50	$53.50
Purchase #6	$86.36	4.712%	$90.4293	$90.43	$90.45	$90.40
Purchase #7	$155.31	4.710%	$162.6251	$162.63	$162.65	$162.60
7 purchase totals =	$801.15		$855.3502	$855.35	$855.40	$855.20