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	$180.28	7.533%	$193.8605	$193.86	$193.85	$193.90
Purchase #2	$198.71	6.738%	$212.0991	$212.10	$212.10	$212.10
Purchase #3	$145.89	4.500%	$152.4551	$152.46	$152.45	$152.50
Purchase #4	$237.78	5.720%	$251.381	$251.38	$251.40	$251.40
Purchase #5	$92.57	10.472%	$102.2639	$102.26	$102.25	$102.30
Purchase #6	$229.31	11.231%	$255.0638	$255.06	$255.05	$255.10
Purchase #7	$74.74	10.752%	$82.776	$82.78	$82.80	$82.80
7 purchase totals =	$1,159.28		$1,249.8994	$1,249.90	$1,249.90	$1,250.10