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	$116.80	12.190%	$131.0379	$131.04	$131.05	$131.00
Purchase #2	$42.98	6.648%	$45.8373	$45.84	$45.85	$45.80
Purchase #3	$179.79	3.791%	$186.6058	$186.61	$186.60	$186.60
Purchase #4	$104.52	11.125%	$116.1479	$116.15	$116.15	$116.10
Purchase #5	$92.61	6.527%	$98.6547	$98.65	$98.65	$98.70
Purchase #6	$35.86	5.810%	$37.9435	$37.94	$37.95	$37.90
Purchase #7	$81.82	3.556%	$84.7295	$84.73	$84.75	$84.70
7 purchase totals =	$654.38		$700.9566	$700.96	$701.00	$700.80