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	$144.51	7.115%	$154.7919	$154.79	$154.80	$154.80
Purchase #2	$39.88	8.724%	$43.3591	$43.36	$43.35	$43.40
Purchase #3	$19.30	11.518%	$21.523	$21.52	$21.50	$21.50
Purchase #4	$95.59	4.474%	$99.8667	$99.87	$99.85	$99.90
Purchase #5	$206.41	8.219%	$223.3748	$223.37	$223.35	$223.40
Purchase #6	$28.51	10.372%	$31.4671	$31.47	$31.45	$31.50
Purchase #7	$126.53	4.748%	$132.5376	$132.54	$132.55	$132.50
7 purchase totals =	$660.73		$706.9202	$706.92	$706.85	$707.00