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	$153.86	11.218%	$171.12	$171.12	$171.10	$171.10
Purchase #2	$68.77	13.440%	$78.0127	$78.01	$78.00	$78.00
Purchase #3	$158.70	8.305%	$171.88	$171.88	$171.90	$171.90
Purchase #4	$191.80	3.794%	$199.0769	$199.08	$199.10	$199.10
Purchase #5	$233.39	13.124%	$264.0201	$264.02	$264.00	$264.00
Purchase #6	$127.63	13.329%	$144.6418	$144.64	$144.65	$144.60
Purchase #7	$17.85	12.158%	$20.0202	$20.02	$20.00	$20.00
7 purchase totals =	$952.00		$1,048.7717	$1,048.77	$1,048.75	$1,048.70