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	$131.28	4.202%	$136.7964	$136.80	$136.80	$136.80
Purchase #2	$188.48	4.192%	$196.3811	$196.38	$196.40	$196.40
Purchase #3	$233.28	9.293%	$254.9587	$254.96	$254.95	$255.00
Purchase #4	$77.84	11.141%	$86.5122	$86.51	$86.50	$86.50
Purchase #5	$198.87	7.478%	$213.7415	$213.74	$213.75	$213.70
Purchase #6	$148.25	7.687%	$159.646	$159.65	$159.65	$159.60
Purchase #7	$104.63	6.450%	$111.3786	$111.38	$111.40	$111.40
7 purchase totals =	$1,082.63		$1,159.4145	$1,159.42	$1,159.45	$1,159.40