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	$209.60	6.489%	$223.2009	$223.20	$223.20	$223.20
Purchase #2	$57.99	5.375%	$61.107	$61.11	$61.10	$61.10
Purchase #3	$215.91	3.200%	$222.8191	$222.82	$222.80	$222.80
Purchase #4	$41.63	6.833%	$44.4746	$44.47	$44.45	$44.50
Purchase #5	$76.59	11.836%	$85.6552	$85.66	$85.65	$85.70
Purchase #6	$220.60	9.740%	$242.0864	$242.09	$242.10	$242.10
Purchase #7	$82.91	8.649%	$90.0809	$90.08	$90.10	$90.10
7 purchase totals =	$905.23		$969.4241	$969.43	$969.40	$969.50