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	$150.82	12.226%	$169.2593	$169.26	$169.25	$169.30
Purchase #2	$210.46	5.725%	$222.5088	$222.51	$222.50	$222.50
Purchase #3	$190.36	5.860%	$201.5151	$201.52	$201.50	$201.50
Purchase #4	$54.83	11.808%	$61.3043	$61.30	$61.30	$61.30
Purchase #5	$86.47	5.695%	$91.3945	$91.39	$91.40	$91.40
Purchase #6	$165.83	7.717%	$178.6271	$178.63	$178.65	$178.60
Purchase #7	$94.35	11.730%	$105.4173	$105.42	$105.40	$105.40
7 purchase totals =	$953.12		$1,030.0264	$1,030.03	$1,030.00	$1,030.00