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	$127.67	4.744%	$133.7267	$133.73	$133.75	$133.70
Purchase #2	$183.93	4.140%	$191.5447	$191.54	$191.55	$191.50
Purchase #3	$86.63	10.717%	$95.9141	$95.91	$95.90	$95.90
Purchase #4	$81.28	11.794%	$90.8662	$90.87	$90.85	$90.90
Purchase #5	$94.73	3.519%	$98.0635	$98.06	$98.05	$98.10
Purchase #6	$224.53	4.460%	$234.544	$234.54	$234.55	$234.50
Purchase #7	$65.81	10.391%	$72.6483	$72.65	$72.65	$72.60
7 purchase totals =	$864.58		$917.3075	$917.30	$917.30	$917.20