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	$100.85	13.664%	$114.6301	$114.63	$114.65	$114.60
Purchase #2	$47.39	12.694%	$53.4057	$53.41	$53.40	$53.40
Purchase #3	$152.48	12.716%	$171.8694	$171.87	$171.85	$171.90
Purchase #4	$189.66	10.526%	$209.6236	$209.62	$209.60	$209.60
Purchase #5	$222.91	9.136%	$243.2751	$243.28	$243.30	$243.30
Purchase #6	$133.94	6.300%	$142.3782	$142.38	$142.40	$142.40
Purchase #7	$133.75	3.551%	$138.4995	$138.50	$138.50	$138.50
7 purchase totals =	$980.98		$1,073.6816	$1,073.69	$1,073.70	$1,073.70