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	$236.88	3.685%	$245.609	$245.61	$245.60	$245.60
Purchase #2	$139.81	11.353%	$155.6826	$155.68	$155.70	$155.70
Purchase #3	$120.47	6.188%	$127.9247	$127.92	$127.90	$127.90
Purchase #4	$136.82	4.447%	$142.9044	$142.90	$142.90	$142.90
Purchase #5	$230.86	12.201%	$259.0272	$259.03	$259.05	$259.00
Purchase #6	$103.56	6.705%	$110.5037	$110.50	$110.50	$110.50
Purchase #7	$59.76	3.664%	$61.9496	$61.95	$61.95	$61.90
7 purchase totals =	$1,028.16		$1,103.6012	$1,103.59	$1,103.60	$1,103.50