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	$82.41	4.243%	$85.9067	$85.91	$85.90	$85.90
Purchase #2	$158.80	4.852%	$166.505	$166.51	$166.50	$166.50
Purchase #3	$113.49	6.108%	$120.422	$120.42	$120.40	$120.40
Purchase #4	$50.41	12.850%	$56.8877	$56.89	$56.90	$56.90
Purchase #5	$136.79	3.862%	$142.0728	$142.07	$142.05	$142.10
Purchase #6	$145.97	7.349%	$156.6973	$156.70	$156.70	$156.70
Purchase #7	$37.32	3.699%	$38.7005	$38.70	$38.70	$38.70
7 purchase totals =	$725.19		$767.1920	$767.20	$767.15	$767.20