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	$184.95	7.415%	$198.664	$198.66	$198.65	$198.70
Purchase #2	$201.52	13.617%	$228.961	$228.96	$228.95	$229.00
Purchase #3	$43.38	11.640%	$48.4294	$48.43	$48.45	$48.40
Purchase #4	$90.93	7.204%	$97.4806	$97.48	$97.50	$97.50
Purchase #5	$139.48	9.611%	$152.8854	$152.89	$152.90	$152.90
Purchase #6	$130.42	6.705%	$139.1647	$139.16	$139.15	$139.20
Purchase #7	$102.43	9.874%	$112.5439	$112.54	$112.55	$112.50
7 purchase totals =	$893.11		$978.1290	$978.12	$978.15	$978.20