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	$47.65	3.741%	$49.4326	$49.43	$49.45	$49.40
Purchase #2	$81.52	5.834%	$86.2759	$86.28	$86.30	$86.30
Purchase #3	$34.71	8.496%	$37.659	$37.66	$37.65	$37.70
Purchase #4	$62.90	7.109%	$67.3716	$67.37	$67.35	$67.40
Purchase #5	$45.39	13.458%	$51.4986	$51.50	$51.50	$51.50
Purchase #6	$66.69	9.815%	$73.2356	$73.24	$73.25	$73.20
Purchase #7	$46.96	9.187%	$51.2742	$51.27	$51.25	$51.30
7 purchase totals =	$385.82		$416.7475	$416.75	$416.75	$416.80