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	$96.68	6.634%	$103.0938	$103.09	$103.10	$103.10
Purchase #2	$142.36	10.347%	$157.09	$157.09	$157.10	$157.10
Purchase #3	$130.57	9.329%	$142.7509	$142.75	$142.75	$142.80
Purchase #4	$138.39	12.214%	$155.293	$155.29	$155.30	$155.30
Purchase #5	$191.34	8.856%	$208.2851	$208.29	$208.30	$208.30
Purchase #6	$171.89	8.131%	$185.8664	$185.87	$185.85	$185.90
Purchase #7	$131.37	8.649%	$142.7322	$142.73	$142.75	$142.70
7 purchase totals =	$1,002.60		$1,095.1114	$1,095.11	$1,095.15	$1,095.20