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	$124.61	13.545%	$141.4884	$141.49	$141.50	$141.50
Purchase #2	$42.94	9.364%	$46.9609	$46.96	$46.95	$47.00
Purchase #3	$237.62	11.839%	$265.7518	$265.75	$265.75	$265.80
Purchase #4	$54.32	10.217%	$59.8699	$59.87	$59.85	$59.90
Purchase #5	$176.61	13.423%	$200.3164	$200.32	$200.30	$200.30
Purchase #6	$235.99	11.476%	$263.0722	$263.07	$263.05	$263.10
Purchase #7	$22.53	4.740%	$23.5979	$23.60	$23.60	$23.60
7 purchase totals =	$894.62		$1,001.0575	$1,001.06	$1,001.00	$1,001.20