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	$40.82	5.802%	$43.1884	$43.19	$43.20	$43.20
Purchase #2	$71.27	9.753%	$78.221	$78.22	$78.20	$78.20
Purchase #3	$147.63	12.664%	$166.3259	$166.33	$166.35	$166.30
Purchase #4	$189.92	13.224%	$215.035	$215.04	$215.05	$215.00
Purchase #5	$202.41	4.193%	$210.8971	$210.90	$210.90	$210.90
Purchase #6	$77.30	6.503%	$82.3268	$82.33	$82.35	$82.30
Purchase #7	$185.67	13.758%	$211.2145	$211.21	$211.20	$211.20
7 purchase totals =	$915.02		$1,007.2087	$1,007.22	$1,007.25	$1,007.10