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	$131.50	6.540%	$140.1001	$140.10	$140.10	$140.10
Purchase #2	$216.97	11.584%	$242.1038	$242.10	$242.10	$242.10
Purchase #3	$92.41	13.606%	$104.9833	$104.98	$105.00	$105.00
Purchase #4	$171.67	10.499%	$189.6936	$189.69	$189.70	$189.70
Purchase #5	$175.67	9.648%	$192.6186	$192.62	$192.60	$192.60
Purchase #6	$89.74	7.661%	$96.615	$96.62	$96.60	$96.60
Purchase #7	$41.56	10.810%	$46.0526	$46.05	$46.05	$46.10
7 purchase totals =	$919.52		$1,012.1670	$1,012.16	$1,012.15	$1,012.20