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	$188.69	4.330%	$196.8603	$196.86	$196.85	$196.90
Purchase #2	$160.54	11.702%	$179.3264	$179.33	$179.35	$179.30
Purchase #3	$237.81	9.599%	$260.6374	$260.64	$260.65	$260.60
Purchase #4	$124.72	11.250%	$138.751	$138.75	$138.75	$138.80
Purchase #5	$78.95	13.481%	$89.5932	$89.59	$89.60	$89.60
Purchase #6	$165.45	8.454%	$179.4371	$179.44	$179.45	$179.40
Purchase #7	$208.84	13.474%	$236.9791	$236.98	$237.00	$237.00
7 purchase totals =	$1,165.00		$1,281.5845	$1,281.59	$1,281.65	$1,281.60