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	$147.40	11.549%	$164.4232	$164.42	$164.40	$164.40
Purchase #2	$61.87	5.475%	$65.2574	$65.26	$65.25	$65.30
Purchase #3	$184.70	5.310%	$194.5076	$194.51	$194.50	$194.50
Purchase #4	$205.77	7.147%	$220.4764	$220.48	$220.50	$220.50
Purchase #5	$239.27	7.337%	$256.8252	$256.83	$256.85	$256.80
Purchase #6	$26.55	8.687%	$28.8564	$28.86	$28.85	$28.90
Purchase #7	$40.74	5.218%	$42.8658	$42.87	$42.85	$42.90
7 purchase totals =	$906.30		$973.2120	$973.23	$973.20	$973.30