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	$232.96	13.441%	$264.2722	$264.27	$264.25	$264.30
Purchase #2	$246.71	6.631%	$263.0693	$263.07	$263.05	$263.10
Purchase #3	$166.59	11.781%	$186.216	$186.22	$186.20	$186.20
Purchase #4	$74.73	4.665%	$78.2162	$78.22	$78.20	$78.20
Purchase #5	$239.76	9.650%	$262.8968	$262.90	$262.90	$262.90
Purchase #6	$191.95	12.153%	$215.2777	$215.28	$215.30	$215.30
Purchase #7	$173.30	4.714%	$181.4694	$181.47	$181.45	$181.50
7 purchase totals =	$1,326.00		$1,451.4176	$1,451.43	$1,451.35	$1,451.50