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	$221.54	5.389%	$233.4788	$233.48	$233.50	$233.50
Purchase #2	$142.77	6.687%	$152.317	$152.32	$152.30	$152.30
Purchase #3	$168.37	8.606%	$182.8599	$182.86	$182.85	$182.90
Purchase #4	$121.96	4.229%	$127.1177	$127.12	$127.10	$127.10
Purchase #5	$149.68	9.659%	$164.1376	$164.14	$164.15	$164.10
Purchase #6	$226.76	8.724%	$246.5425	$246.54	$246.55	$246.50
Purchase #7	$165.99	3.325%	$171.5092	$171.51	$171.50	$171.50
7 purchase totals =	$1,197.07		$1,277.9627	$1,277.97	$1,277.95	$1,277.90