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	$111.76	13.614%	$126.975	$126.98	$127.00	$127.00
Purchase #2	$136.93	6.251%	$145.4895	$145.49	$145.50	$145.50
Purchase #3	$205.38	7.622%	$221.0341	$221.03	$221.05	$221.00
Purchase #4	$40.39	12.422%	$45.4072	$45.41	$45.40	$45.40
Purchase #5	$86.69	7.571%	$93.2533	$93.25	$93.25	$93.30
Purchase #6	$124.60	7.263%	$133.6497	$133.65	$133.65	$133.60
Purchase #7	$194.56	9.346%	$212.7436	$212.74	$212.75	$212.70
7 purchase totals =	$900.31		$978.5524	$978.55	$978.60	$978.50