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	$181.73	10.315%	$200.4754	$200.48	$200.50	$200.50
Purchase #2	$129.75	9.751%	$142.4019	$142.40	$142.40	$142.40
Purchase #3	$53.45	4.490%	$55.8499	$55.85	$55.85	$55.80
Purchase #4	$243.72	13.275%	$276.0738	$276.07	$276.05	$276.10
Purchase #5	$86.69	4.663%	$90.7324	$90.73	$90.75	$90.70
Purchase #6	$231.51	9.441%	$253.3669	$253.37	$253.35	$253.40
Purchase #7	$241.65	11.591%	$269.6597	$269.66	$269.65	$269.70
7 purchase totals =	$1,168.50		$1,288.5600	$1,288.56	$1,288.55	$1,288.60