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	$92.45	4.390%	$96.5086	$96.51	$96.50	$96.50
Purchase #2	$176.46	4.479%	$184.3636	$184.36	$184.35	$184.40
Purchase #3	$37.95	5.618%	$40.082	$40.08	$40.10	$40.10
Purchase #4	$147.83	13.607%	$167.9452	$167.95	$167.95	$167.90
Purchase #5	$11.88	3.801%	$12.3316	$12.33	$12.35	$12.30
Purchase #6	$58.36	12.715%	$65.7805	$65.78	$65.80	$65.80
Purchase #7	$122.64	11.119%	$136.2763	$136.28	$136.30	$136.30
7 purchase totals =	$647.57		$703.2878	$703.29	$703.35	$703.30