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	$121.30	8.767%	$131.9344	$131.93	$131.95	$131.90
Purchase #2	$91.78	5.222%	$96.5728	$96.57	$96.55	$96.60
Purchase #3	$228.32	6.314%	$242.7361	$242.74	$242.75	$242.70
Purchase #4	$231.56	11.242%	$257.592	$257.59	$257.60	$257.60
Purchase #5	$88.43	12.191%	$99.2105	$99.21	$99.20	$99.20
Purchase #6	$98.54	9.771%	$108.1683	$108.17	$108.15	$108.20
Purchase #7	$155.78	4.419%	$162.6639	$162.66	$162.65	$162.70
7 purchase totals =	$1,015.71		$1,098.8780	$1,098.87	$1,098.85	$1,098.90