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	$152.35	11.402%	$169.7209	$169.72	$169.70	$169.70
Purchase #2	$40.36	5.652%	$42.6411	$42.64	$42.65	$42.60
Purchase #3	$6.61	12.549%	$7.4395	$7.44	$7.45	$7.40
Purchase #4	$188.60	6.457%	$200.7779	$200.78	$200.80	$200.80
Purchase #5	$41.55	9.156%	$45.3543	$45.35	$45.35	$45.40
Purchase #6	$210.86	4.536%	$220.4246	$220.42	$220.40	$220.40
Purchase #7	$59.89	7.797%	$64.5596	$64.56	$64.55	$64.60
7 purchase totals =	$700.22		$750.9179	$750.91	$750.90	$750.90