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	$150.97	10.661%	$167.0649	$167.06	$167.05	$167.10
Purchase #2	$75.42	4.143%	$78.5447	$78.54	$78.55	$78.50
Purchase #3	$91.75	8.200%	$99.2735	$99.27	$99.25	$99.30
Purchase #4	$85.31	3.474%	$88.2737	$88.27	$88.25	$88.30
Purchase #5	$169.27	7.417%	$181.8248	$181.82	$181.80	$181.80
Purchase #6	$97.88	11.604%	$109.238	$109.24	$109.25	$109.20
Purchase #7	$143.73	12.153%	$161.1975	$161.20	$161.20	$161.20
7 purchase totals =	$814.33		$885.4171	$885.40	$885.35	$885.40