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	$86.99	12.154%	$97.5628	$97.56	$97.55	$97.60
Purchase #2	$40.37	8.397%	$43.7599	$43.76	$43.75	$43.80
Purchase #3	$212.54	4.180%	$221.4242	$221.42	$221.40	$221.40
Purchase #4	$179.79	3.381%	$185.8687	$185.87	$185.85	$185.90
Purchase #5	$100.82	9.244%	$110.1398	$110.14	$110.15	$110.10
Purchase #6	$148.92	10.143%	$164.025	$164.03	$164.05	$164.00
Purchase #7	$246.77	3.693%	$255.8832	$255.88	$255.90	$255.90
7 purchase totals =	$1,016.20		$1,078.6636	$1,078.66	$1,078.65	$1,078.70