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	$221.29	8.597%	$240.3143	$240.31	$240.30	$240.30
Purchase #2	$79.81	8.866%	$86.886	$86.89	$86.90	$86.90
Purchase #3	$213.83	11.680%	$238.8053	$238.81	$238.80	$238.80
Purchase #4	$246.87	11.323%	$274.8231	$274.82	$274.80	$274.80
Purchase #5	$168.41	11.858%	$188.3801	$188.38	$188.40	$188.40
Purchase #6	$76.91	12.775%	$86.7353	$86.74	$86.75	$86.70
Purchase #7	$97.40	8.675%	$105.8495	$105.85	$105.85	$105.80
7 purchase totals =	$1,104.52		$1,221.7936	$1,221.80	$1,221.80	$1,221.70