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	$205.84	6.715%	$219.6622	$219.66	$219.65	$219.70
Purchase #2	$151.63	11.361%	$168.8567	$168.86	$168.85	$168.90
Purchase #3	$99.76	9.174%	$108.912	$108.91	$108.90	$108.90
Purchase #4	$133.94	6.832%	$143.0908	$143.09	$143.10	$143.10
Purchase #5	$127.76	13.752%	$145.3296	$145.33	$145.35	$145.30
Purchase #6	$170.33	8.708%	$185.1623	$185.16	$185.15	$185.20
Purchase #7	$191.85	4.293%	$200.0861	$200.09	$200.10	$200.10
7 purchase totals =	$1,081.11		$1,171.0997	$1,171.10	$1,171.10	$1,171.20