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	$222.89	6.373%	$237.0948	$237.09	$237.10	$237.10
Purchase #2	$134.36	5.755%	$142.0924	$142.09	$142.10	$142.10
Purchase #3	$98.57	8.415%	$106.8647	$106.86	$106.85	$106.90
Purchase #4	$194.29	7.373%	$208.615	$208.62	$208.60	$208.60
Purchase #5	$35.39	6.287%	$37.615	$37.62	$37.60	$37.60
Purchase #6	$121.80	12.578%	$137.12	$137.12	$137.10	$137.10
Purchase #7	$133.62	11.378%	$148.8233	$148.82	$148.80	$148.80
7 purchase totals =	$940.92		$1,018.2252	$1,018.22	$1,018.15	$1,018.20