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	$138.36	3.247%	$142.8525	$142.85	$142.85	$142.90
Purchase #2	$155.64	4.337%	$162.3901	$162.39	$162.40	$162.40
Purchase #3	$103.55	5.380%	$109.121	$109.12	$109.10	$109.10
Purchase #4	$225.89	10.724%	$250.1144	$250.11	$250.10	$250.10
Purchase #5	$180.33	9.567%	$197.5822	$197.58	$197.60	$197.60
Purchase #6	$34.65	8.190%	$37.4878	$37.49	$37.50	$37.50
Purchase #7	$187.74	3.783%	$194.8422	$194.84	$194.85	$194.80
7 purchase totals =	$1,026.16		$1,094.3902	$1,094.38	$1,094.40	$1,094.40