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	$97.88	6.121%	$103.8712	$103.87	$103.85	$103.90
Purchase #2	$234.88	13.334%	$266.1989	$266.20	$266.20	$266.20
Purchase #3	$19.30	4.790%	$20.2245	$20.22	$20.20	$20.20
Purchase #4	$57.46	9.219%	$62.7572	$62.76	$62.75	$62.80
Purchase #5	$171.78	13.239%	$194.522	$194.52	$194.50	$194.50
Purchase #6	$228.54	4.450%	$238.71	$238.71	$238.70	$238.70
Purchase #7	$208.76	13.448%	$236.834	$236.83	$236.85	$236.80
7 purchase totals =	$1,018.60		$1,123.1178	$1,123.11	$1,123.05	$1,123.10