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	$25.75	8.367%	$27.9045	$27.90	$27.90	$27.90
Purchase #2	$6.62	11.212%	$7.3622	$7.36	$7.35	$7.40
Purchase #3	$96.64	3.823%	$100.3345	$100.33	$100.35	$100.30
Purchase #4	$222.93	9.786%	$244.7459	$244.75	$244.75	$244.70
Purchase #5	$248.49	4.192%	$258.9067	$258.91	$258.90	$258.90
Purchase #6	$244.52	12.436%	$274.9285	$274.93	$274.95	$274.90
Purchase #7	$96.69	3.583%	$100.1544	$100.15	$100.15	$100.20
7 purchase totals =	$941.64		$1,014.3367	$1,014.33	$1,014.35	$1,014.30