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	$208.28	3.589%	$215.7552	$215.76	$215.75	$215.80
Purchase #2	$152.84	11.149%	$169.8801	$169.88	$169.90	$169.90
Purchase #3	$153.82	13.734%	$174.9456	$174.95	$174.95	$174.90
Purchase #4	$81.72	3.388%	$84.4887	$84.49	$84.50	$84.50
Purchase #5	$148.55	12.808%	$167.5763	$167.58	$167.60	$167.60
Purchase #6	$229.89	11.156%	$255.5365	$255.54	$255.55	$255.50
Purchase #7	$99.49	13.860%	$113.2793	$113.28	$113.30	$113.30
7 purchase totals =	$1,074.59		$1,181.4617	$1,181.48	$1,181.55	$1,181.50