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	$189.36	12.517%	$213.0622	$213.06	$213.05	$213.10
Purchase #2	$87.34	3.642%	$90.5209	$90.52	$90.50	$90.50
Purchase #3	$150.66	13.589%	$171.1332	$171.13	$171.15	$171.10
Purchase #4	$90.59	12.678%	$102.075	$102.08	$102.10	$102.10
Purchase #5	$58.72	11.166%	$65.2767	$65.28	$65.30	$65.30
Purchase #6	$66.54	3.631%	$68.9561	$68.96	$68.95	$69.00
Purchase #7	$86.81	11.373%	$96.6829	$96.68	$96.70	$96.70
7 purchase totals =	$730.02		$807.7070	$807.71	$807.75	$807.80