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	$167.65	10.536%	$185.3136	$185.31	$185.30	$185.30
Purchase #2	$157.66	6.524%	$167.9457	$167.95	$167.95	$167.90
Purchase #3	$84.83	5.734%	$89.6942	$89.69	$89.70	$89.70
Purchase #4	$201.83	5.766%	$213.4675	$213.47	$213.45	$213.50
Purchase #5	$66.40	10.274%	$73.2219	$73.22	$73.20	$73.20
Purchase #6	$100.83	6.272%	$107.1541	$107.15	$107.15	$107.20
Purchase #7	$133.98	7.667%	$144.2522	$144.25	$144.25	$144.30
7 purchase totals =	$913.18		$981.0492	$981.04	$981.00	$981.10