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	$68.32	5.206%	$71.8767	$71.88	$71.90	$71.90
Purchase #2	$176.45	4.855%	$185.0166	$185.02	$185.00	$185.00
Purchase #3	$203.84	3.416%	$210.8032	$210.80	$210.80	$210.80
Purchase #4	$119.88	11.336%	$133.4696	$133.47	$133.45	$133.50
Purchase #5	$17.34	12.676%	$19.538	$19.54	$19.55	$19.50
Purchase #6	$159.46	5.869%	$168.8187	$168.82	$168.80	$168.80
Purchase #7	$140.87	8.842%	$153.3257	$153.33	$153.35	$153.30
7 purchase totals =	$886.16		$942.8485	$942.86	$942.85	$942.80