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	$243.49	7.730%	$262.3118	$262.31	$262.30	$262.30
Purchase #2	$162.51	5.409%	$171.3002	$171.30	$171.30	$171.30
Purchase #3	$111.44	4.456%	$116.4058	$116.41	$116.40	$116.40
Purchase #4	$99.41	10.382%	$109.7307	$109.73	$109.75	$109.70
Purchase #5	$141.84	13.673%	$161.2338	$161.23	$161.25	$161.20
Purchase #6	$12.46	3.711%	$12.9224	$12.92	$12.90	$12.90
Purchase #7	$75.41	7.128%	$80.7852	$80.79	$80.80	$80.80
7 purchase totals =	$846.56		$914.6899	$914.69	$914.70	$914.60