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	$191.73	10.585%	$212.0246	$212.02	$212.00	$212.00
Purchase #2	$49.45	10.451%	$54.618	$54.62	$54.60	$54.60
Purchase #3	$186.55	12.103%	$209.1281	$209.13	$209.15	$209.10
Purchase #4	$78.77	13.804%	$89.6434	$89.64	$89.65	$89.60
Purchase #5	$205.43	9.656%	$225.2663	$225.27	$225.25	$225.30
Purchase #6	$84.92	12.714%	$95.7167	$95.72	$95.70	$95.70
Purchase #7	$35.76	12.392%	$40.1914	$40.19	$40.20	$40.20
7 purchase totals =	$832.61		$926.5885	$926.59	$926.55	$926.50