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	$183.42	3.793%	$190.3771	$190.38	$190.40	$190.40
Purchase #2	$105.86	10.628%	$117.1108	$117.11	$117.10	$117.10
Purchase #3	$55.98	6.731%	$59.748	$59.75	$59.75	$59.70
Purchase #4	$108.56	5.603%	$114.6426	$114.64	$114.65	$114.60
Purchase #5	$158.56	13.705%	$180.2906	$180.29	$180.30	$180.30
Purchase #6	$159.82	5.151%	$168.0523	$168.05	$168.05	$168.10
Purchase #7	$42.26	12.730%	$47.6397	$47.64	$47.65	$47.60
7 purchase totals =	$814.46		$877.8611	$877.86	$877.90	$877.80