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	$113.95	11.497%	$127.0508	$127.05	$127.05	$127.10
Purchase #2	$152.75	7.619%	$164.388	$164.39	$164.40	$164.40
Purchase #3	$32.57	11.598%	$36.3475	$36.35	$36.35	$36.30
Purchase #4	$186.63	4.459%	$194.9518	$194.95	$194.95	$195.00
Purchase #5	$76.31	3.301%	$78.829	$78.83	$78.85	$78.80
Purchase #6	$107.73	3.772%	$111.7936	$111.79	$111.80	$111.80
Purchase #7	$156.39	6.271%	$166.1972	$166.20	$166.20	$166.20
7 purchase totals =	$826.33		$879.5579	$879.56	$879.60	$879.60