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	$205.41	12.765%	$231.6306	$231.63	$231.65	$231.60
Purchase #2	$62.67	13.466%	$71.1091	$71.11	$71.10	$71.10
Purchase #3	$23.69	9.471%	$25.9337	$25.93	$25.95	$25.90
Purchase #4	$116.58	9.485%	$127.6376	$127.64	$127.65	$127.60
Purchase #5	$147.39	11.271%	$164.0023	$164.00	$164.00	$164.00
Purchase #6	$96.68	5.389%	$101.8901	$101.89	$101.90	$101.90
Purchase #7	$228.76	11.856%	$255.8818	$255.88	$255.90	$255.90
7 purchase totals =	$881.18		$978.0852	$978.08	$978.15	$978.00