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	$56.41	9.599%	$61.8248	$61.82	$61.80	$61.80
Purchase #2	$134.38	5.194%	$141.3597	$141.36	$141.35	$141.40
Purchase #3	$193.71	8.253%	$209.6969	$209.70	$209.70	$209.70
Purchase #4	$150.85	7.860%	$162.7068	$162.71	$162.70	$162.70
Purchase #5	$134.39	9.742%	$147.4823	$147.48	$147.50	$147.50
Purchase #6	$148.84	12.398%	$167.2932	$167.29	$167.30	$167.30
Purchase #7	$225.51	13.218%	$255.3179	$255.32	$255.30	$255.30
7 purchase totals =	$1,044.09		$1,145.6816	$1,145.68	$1,145.65	$1,145.70