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	$148.88	12.872%	$168.0438	$168.04	$168.05	$168.00
Purchase #2	$150.76	3.868%	$156.5914	$156.59	$156.60	$156.60
Purchase #3	$113.81	8.579%	$123.5738	$123.57	$123.55	$123.60
Purchase #4	$218.75	9.219%	$238.9166	$238.92	$238.90	$238.90
Purchase #5	$181.62	6.404%	$193.2509	$193.25	$193.25	$193.30
Purchase #6	$224.46	11.174%	$249.5412	$249.54	$249.55	$249.50
Purchase #7	$74.37	5.378%	$78.3696	$78.37	$78.35	$78.40
7 purchase totals =	$1,112.65		$1,208.2873	$1,208.28	$1,208.25	$1,208.30