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	$133.69	12.828%	$150.8398	$150.84	$150.85	$150.80
Purchase #2	$71.64	6.811%	$76.5194	$76.52	$76.50	$76.50
Purchase #3	$157.97	6.185%	$167.7404	$167.74	$167.75	$167.70
Purchase #4	$156.33	12.818%	$176.3684	$176.37	$176.35	$176.40
Purchase #5	$238.85	6.540%	$254.4708	$254.47	$254.45	$254.50
Purchase #6	$120.98	9.210%	$132.1223	$132.12	$132.10	$132.10
Purchase #7	$55.98	5.611%	$59.121	$59.12	$59.10	$59.10
7 purchase totals =	$935.44		$1,017.1821	$1,017.18	$1,017.10	$1,017.10