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	$22.91	10.575%	$25.3327	$25.33	$25.35	$25.30
Purchase #2	$201.73	13.688%	$229.3428	$229.34	$229.35	$229.30
Purchase #3	$141.25	7.672%	$152.0867	$152.09	$152.10	$152.10
Purchase #4	$218.78	12.436%	$245.9875	$245.99	$246.00	$246.00
Purchase #5	$145.66	4.622%	$152.3924	$152.39	$152.40	$152.40
Purchase #6	$54.86	13.575%	$62.3072	$62.31	$62.30	$62.30
Purchase #7	$154.54	8.109%	$167.0716	$167.07	$167.05	$167.10
7 purchase totals =	$939.73		$1,034.5209	$1,034.52	$1,034.55	$1,034.50