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	$62.91	4.284%	$65.6051	$65.61	$65.60	$65.60
Purchase #2	$12.76	5.732%	$13.4914	$13.49	$13.50	$13.50
Purchase #3	$173.64	13.539%	$197.1491	$197.15	$197.15	$197.10
Purchase #4	$244.27	5.457%	$257.5998	$257.60	$257.60	$257.60
Purchase #5	$199.83	9.357%	$218.5281	$218.53	$218.55	$218.50
Purchase #6	$165.92	3.263%	$171.334	$171.33	$171.35	$171.30
Purchase #7	$76.79	8.617%	$83.407	$83.41	$83.40	$83.40
7 purchase totals =	$936.12		$1,007.1145	$1,007.12	$1,007.15	$1,007.00