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	$169.91	11.334%	$189.1676	$189.17	$189.15	$189.20
Purchase #2	$73.28	4.271%	$76.4098	$76.41	$76.40	$76.40
Purchase #3	$149.25	12.489%	$167.8898	$167.89	$167.90	$167.90
Purchase #4	$228.47	9.436%	$250.0284	$250.03	$250.05	$250.00
Purchase #5	$210.94	7.873%	$227.5473	$227.55	$227.55	$227.50
Purchase #6	$71.36	10.114%	$78.5774	$78.58	$78.60	$78.60
Purchase #7	$165.66	5.484%	$174.7448	$174.74	$174.75	$174.70
7 purchase totals =	$1,068.87		$1,164.3651	$1,164.37	$1,164.40	$1,164.30