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	$115.91	9.648%	$127.093	$127.09	$127.10	$127.10
Purchase #2	$186.72	4.382%	$194.9021	$194.90	$194.90	$194.90
Purchase #3	$35.81	11.259%	$39.8418	$39.84	$39.85	$39.80
Purchase #4	$191.25	10.660%	$211.6373	$211.64	$211.65	$211.60
Purchase #5	$78.71	6.339%	$83.6994	$83.70	$83.70	$83.70
Purchase #6	$244.30	13.725%	$277.8302	$277.83	$277.85	$277.80
Purchase #7	$64.78	6.144%	$68.7601	$68.76	$68.75	$68.80
7 purchase totals =	$917.48		$1,003.7639	$1,003.76	$1,003.80	$1,003.70