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	$211.60	8.361%	$229.2919	$229.29	$229.30	$229.30
Purchase #2	$169.93	12.842%	$191.7524	$191.75	$191.75	$191.80
Purchase #3	$94.25	4.315%	$98.3169	$98.32	$98.30	$98.30
Purchase #4	$132.47	11.318%	$147.463	$147.46	$147.45	$147.50
Purchase #5	$68.35	3.333%	$70.6281	$70.63	$70.65	$70.60
Purchase #6	$79.83	3.108%	$82.3111	$82.31	$82.30	$82.30
Purchase #7	$50.25	12.544%	$56.5534	$56.55	$56.55	$56.60
7 purchase totals =	$806.68		$876.3168	$876.31	$876.30	$876.40