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	$212.50	4.856%	$222.819	$222.82	$222.80	$222.80
Purchase #2	$176.56	7.532%	$189.8585	$189.86	$189.85	$189.90
Purchase #3	$96.89	6.724%	$103.4049	$103.40	$103.40	$103.40
Purchase #4	$129.90	12.289%	$145.8634	$145.86	$145.85	$145.90
Purchase #5	$97.79	3.462%	$101.1755	$101.18	$101.20	$101.20
Purchase #6	$184.30	13.783%	$209.7021	$209.70	$209.70	$209.70
Purchase #7	$73.71	8.696%	$80.1198	$80.12	$80.10	$80.10
7 purchase totals =	$971.65		$1,052.9432	$1,052.94	$1,052.90	$1,053.00