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	$105.67	11.500%	$117.8221	$117.82	$117.80	$117.80
Purchase #2	$32.73	3.611%	$33.9119	$33.91	$33.90	$33.90
Purchase #3	$9.85	4.341%	$10.2776	$10.28	$10.30	$10.30
Purchase #4	$100.51	7.149%	$107.6955	$107.70	$107.70	$107.70
Purchase #5	$223.85	6.344%	$238.051	$238.05	$238.05	$238.10
Purchase #6	$89.82	13.424%	$101.8774	$101.88	$101.90	$101.90
Purchase #7	$195.83	9.867%	$215.1525	$215.15	$215.15	$215.20
7 purchase totals =	$758.26		$824.7880	$824.79	$824.80	$824.90