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	$104.44	8.334%	$113.144	$113.14	$113.15	$113.10
Purchase #2	$138.72	12.498%	$156.0572	$156.06	$156.05	$156.10
Purchase #3	$124.58	13.361%	$141.2251	$141.23	$141.25	$141.20
Purchase #4	$192.75	5.240%	$202.8501	$202.85	$202.85	$202.90
Purchase #5	$10.92	6.220%	$11.5992	$11.60	$11.60	$11.60
Purchase #6	$54.78	12.115%	$61.4166	$61.42	$61.40	$61.40
Purchase #7	$182.32	4.535%	$190.5882	$190.59	$190.60	$190.60
7 purchase totals =	$808.51		$876.8804	$876.89	$876.90	$876.90