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	$164.29	5.504%	$173.3325	$173.33	$173.35	$173.30
Purchase #2	$56.81	10.601%	$62.8324	$62.83	$62.85	$62.80
Purchase #3	$186.90	11.768%	$208.8944	$208.89	$208.90	$208.90
Purchase #4	$215.81	11.281%	$240.1555	$240.16	$240.15	$240.20
Purchase #5	$97.36	5.104%	$102.3293	$102.33	$102.35	$102.30
Purchase #6	$156.63	12.829%	$176.7241	$176.72	$176.70	$176.70
Purchase #7	$43.32	6.148%	$45.9833	$45.98	$46.00	$46.00
7 purchase totals =	$921.12		$1,010.2515	$1,010.24	$1,010.30	$1,010.20