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	$176.42	3.214%	$182.0901	$182.09	$182.10	$182.10
Purchase #2	$96.89	10.574%	$107.1351	$107.14	$107.15	$107.10
Purchase #3	$42.85	5.620%	$45.2582	$45.26	$45.25	$45.30
Purchase #4	$139.95	11.551%	$156.1156	$156.12	$156.10	$156.10
Purchase #5	$141.78	13.541%	$160.9784	$160.98	$161.00	$161.00
Purchase #6	$218.83	5.666%	$231.2289	$231.23	$231.25	$231.20
Purchase #7	$35.69	13.271%	$40.4264	$40.43	$40.45	$40.40
7 purchase totals =	$852.41		$923.2327	$923.25	$923.30	$923.20