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	$55.27	11.341%	$61.5382	$61.54	$61.55	$61.50
Purchase #2	$125.86	11.354%	$140.1501	$140.15	$140.15	$140.20
Purchase #3	$29.59	8.285%	$32.0415	$32.04	$32.05	$32.00
Purchase #4	$57.99	6.503%	$61.7611	$61.76	$61.75	$61.80
Purchase #5	$19.62	8.462%	$21.2802	$21.28	$21.30	$21.30
Purchase #6	$85.60	7.410%	$91.943	$91.94	$91.95	$91.90
Purchase #7	$84.45	6.581%	$90.0077	$90.01	$90.00	$90.00
7 purchase totals =	$458.38		$498.7218	$498.72	$498.75	$498.70