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	$27.57	12.695%	$31.07	$31.07	$31.05	$31.10
Purchase #2	$10.71	6.609%	$11.4178	$11.42	$11.40	$11.40
Purchase #3	$59.30	3.377%	$61.3026	$61.30	$61.30	$61.30
Purchase #4	$145.85	7.564%	$156.8821	$156.88	$156.90	$156.90
Purchase #5	$42.40	3.194%	$43.7543	$43.75	$43.75	$43.80
Purchase #6	$150.63	4.860%	$157.9506	$157.95	$157.95	$158.00
Purchase #7	$12.98	11.846%	$14.5176	$14.52	$14.50	$14.50
7 purchase totals =	$449.44		$476.8950	$476.89	$476.85	$477.00