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	$71.86	3.498%	$74.3737	$74.37	$74.35	$74.40
Purchase #2	$196.94	11.426%	$219.4424	$219.44	$219.45	$219.40
Purchase #3	$49.48	6.866%	$52.8773	$52.88	$52.90	$52.90
Purchase #4	$8.33	6.811%	$8.8974	$8.90	$8.90	$8.90
Purchase #5	$16.63	8.320%	$18.0136	$18.01	$18.00	$18.00
Purchase #6	$180.48	9.104%	$196.9109	$196.91	$196.90	$196.90
Purchase #7	$17.53	6.500%	$18.6695	$18.67	$18.65	$18.70
7 purchase totals =	$541.25		$589.1848	$589.18	$589.15	$589.20