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	$32.80	10.335%	$36.1899	$36.19	$36.20	$36.20
Purchase #2	$191.94	3.553%	$198.7596	$198.76	$198.75	$198.80
Purchase #3	$188.70	10.307%	$208.1493	$208.15	$208.15	$208.10
Purchase #4	$215.85	10.537%	$238.5941	$238.59	$238.60	$238.60
Purchase #5	$203.79	3.113%	$210.134	$210.13	$210.15	$210.10
Purchase #6	$55.30	11.853%	$61.8547	$61.85	$61.85	$61.90
Purchase #7	$131.39	9.817%	$144.2886	$144.29	$144.30	$144.30
7 purchase totals =	$1,019.77		$1,097.9702	$1,097.96	$1,098.00	$1,098.00