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	$27.39	3.828%	$28.4385	$28.44	$28.45	$28.40
Purchase #2	$92.52	7.705%	$99.6487	$99.65	$99.65	$99.60
Purchase #3	$88.69	7.834%	$95.638	$95.64	$95.65	$95.60
Purchase #4	$40.89	4.549%	$42.7501	$42.75	$42.75	$42.80
Purchase #5	$218.79	12.483%	$246.1016	$246.10	$246.10	$246.10
Purchase #6	$136.32	6.597%	$145.313	$145.31	$145.30	$145.30
Purchase #7	$16.99	9.822%	$18.6588	$18.66	$18.65	$18.70
7 purchase totals =	$621.59		$676.5487	$676.55	$676.55	$676.50