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	$129.59	9.769%	$142.2496	$142.25	$142.25	$142.20
Purchase #2	$124.67	4.833%	$130.6953	$130.70	$130.70	$130.70
Purchase #3	$105.56	7.265%	$113.2289	$113.23	$113.25	$113.20
Purchase #4	$75.50	4.448%	$78.8582	$78.86	$78.85	$78.90
Purchase #5	$205.41	10.482%	$226.9411	$226.94	$226.95	$226.90
Purchase #6	$27.86	5.737%	$29.4583	$29.46	$29.45	$29.50
Purchase #7	$59.91	12.417%	$67.349	$67.35	$67.35	$67.30
7 purchase totals =	$728.50		$788.7804	$788.79	$788.80	$788.70