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	$223.83	7.304%	$240.1785	$240.18	$240.20	$240.20
Purchase #2	$162.45	3.632%	$168.3502	$168.35	$168.35	$168.40
Purchase #3	$72.86	13.207%	$82.4826	$82.48	$82.50	$82.50
Purchase #4	$118.71	5.522%	$125.2652	$125.27	$125.25	$125.30
Purchase #5	$80.83	4.504%	$84.4706	$84.47	$84.45	$84.50
Purchase #6	$96.26	6.167%	$102.1964	$102.20	$102.20	$102.20
Purchase #7	$51.58	7.174%	$55.2803	$55.28	$55.30	$55.30
7 purchase totals =	$806.52		$858.2238	$858.23	$858.25	$858.40