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	$36.48	13.621%	$41.4489	$41.45	$41.45	$41.40
Purchase #2	$118.25	3.602%	$122.5094	$122.51	$122.50	$122.50
Purchase #3	$200.86	9.453%	$219.8473	$219.85	$219.85	$219.80
Purchase #4	$148.64	7.276%	$159.455	$159.46	$159.45	$159.50
Purchase #5	$149.79	8.194%	$162.0638	$162.06	$162.05	$162.10
Purchase #6	$90.70	9.528%	$99.3419	$99.34	$99.35	$99.30
Purchase #7	$166.50	13.718%	$189.3405	$189.34	$189.35	$189.30
7 purchase totals =	$911.22		$994.0068	$994.01	$994.00	$993.90