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	$54.25	13.626%	$61.6421	$61.64	$61.65	$61.60
Purchase #2	$223.98	3.341%	$231.4632	$231.46	$231.45	$231.50
Purchase #3	$197.28	5.665%	$208.4559	$208.46	$208.45	$208.50
Purchase #4	$187.75	3.587%	$194.4846	$194.48	$194.50	$194.50
Purchase #5	$85.28	7.259%	$91.4705	$91.47	$91.45	$91.50
Purchase #6	$53.69	8.296%	$58.1441	$58.14	$58.15	$58.10
Purchase #7	$140.68	5.666%	$148.6509	$148.65	$148.65	$148.70
7 purchase totals =	$942.91		$994.3113	$994.30	$994.30	$994.40