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	$132.90	8.354%	$144.0025	$144.00	$144.00	$144.00
Purchase #2	$95.39	4.553%	$99.7331	$99.73	$99.75	$99.70
Purchase #3	$13.27	4.409%	$13.8551	$13.86	$13.85	$13.90
Purchase #4	$236.87	3.478%	$245.1083	$245.11	$245.10	$245.10
Purchase #5	$230.63	8.540%	$250.3258	$250.33	$250.35	$250.30
Purchase #6	$249.74	12.136%	$280.0484	$280.05	$280.05	$280.00
Purchase #7	$141.81	3.186%	$146.3281	$146.33	$146.35	$146.30
7 purchase totals =	$1,100.61		$1,179.4013	$1,179.41	$1,179.45	$1,179.30