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	$99.49	7.534%	$106.9856	$106.99	$107.00	$107.00
Purchase #2	$71.78	9.444%	$78.5589	$78.56	$78.55	$78.60
Purchase #3	$35.78	12.493%	$40.25	$40.25	$40.25	$40.30
Purchase #4	$150.55	6.573%	$160.4457	$160.45	$160.45	$160.40
Purchase #5	$31.36	13.754%	$35.6733	$35.67	$35.65	$35.70
Purchase #6	$6.28	10.351%	$6.93	$6.93	$6.95	$6.90
Purchase #7	$146.61	13.546%	$166.4698	$166.47	$166.45	$166.50
7 purchase totals =	$541.85		$595.3133	$595.32	$595.30	$595.40