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	$105.49	8.562%	$114.5221	$114.52	$114.50	$114.50
Purchase #2	$186.40	7.801%	$200.9411	$200.94	$200.95	$200.90
Purchase #3	$103.30	12.690%	$116.4088	$116.41	$116.40	$116.40
Purchase #4	$50.83	8.723%	$55.2639	$55.26	$55.25	$55.30
Purchase #5	$156.79	12.150%	$175.84	$175.84	$175.85	$175.80
Purchase #6	$19.47	9.841%	$21.386	$21.39	$21.40	$21.40
Purchase #7	$166.81	13.687%	$189.6413	$189.64	$189.65	$189.60
7 purchase totals =	$789.09		$874.0032	$874.00	$874.00	$873.90