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	$156.29	11.700%	$174.5759	$174.58	$174.60	$174.60
Purchase #2	$229.65	8.452%	$249.06	$249.06	$249.05	$249.10
Purchase #3	$131.81	8.169%	$142.5776	$142.58	$142.60	$142.60
Purchase #4	$8.59	10.791%	$9.5169	$9.52	$9.50	$9.50
Purchase #5	$179.75	12.180%	$201.6436	$201.64	$201.65	$201.60
Purchase #6	$186.59	5.340%	$196.5539	$196.55	$196.55	$196.60
Purchase #7	$158.88	12.170%	$178.2157	$178.22	$178.20	$178.20
7 purchase totals =	$1,051.56		$1,152.1436	$1,152.15	$1,152.15	$1,152.20