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	$46.29	13.771%	$52.6646	$52.66	$52.65	$52.70
Purchase #2	$71.53	9.573%	$78.3776	$78.38	$78.40	$78.40
Purchase #3	$217.82	3.360%	$225.1388	$225.14	$225.15	$225.10
Purchase #4	$196.96	6.358%	$209.4827	$209.48	$209.50	$209.50
Purchase #5	$165.97	12.392%	$186.537	$186.54	$186.55	$186.50
Purchase #6	$186.89	13.770%	$212.6248	$212.62	$212.60	$212.60
Purchase #7	$153.56	7.148%	$164.5365	$164.54	$164.55	$164.50
7 purchase totals =	$1,039.02		$1,129.3620	$1,129.36	$1,129.40	$1,129.30