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	$16.38	3.152%	$16.8963	$16.90	$16.90	$16.90
Purchase #2	$216.42	3.773%	$224.5855	$224.59	$224.60	$224.60
Purchase #3	$245.74	5.344%	$258.8723	$258.87	$258.85	$258.90
Purchase #4	$85.36	13.813%	$97.1508	$97.15	$97.15	$97.20
Purchase #5	$78.65	4.815%	$82.437	$82.44	$82.45	$82.40
Purchase #6	$152.31	10.706%	$168.6163	$168.62	$168.60	$168.60
Purchase #7	$206.97	8.140%	$223.8174	$223.82	$223.80	$223.80
7 purchase totals =	$1,001.83		$1,072.3756	$1,072.39	$1,072.35	$1,072.40