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	$158.94	5.236%	$167.2621	$167.26	$167.25	$167.30
Purchase #2	$189.83	7.605%	$204.2666	$204.27	$204.25	$204.30
Purchase #3	$223.70	12.328%	$251.2777	$251.28	$251.30	$251.30
Purchase #4	$142.61	13.697%	$162.1433	$162.14	$162.15	$162.10
Purchase #5	$218.94	8.651%	$237.8805	$237.88	$237.90	$237.90
Purchase #6	$142.50	7.538%	$153.2417	$153.24	$153.25	$153.20
Purchase #7	$96.58	3.310%	$99.7768	$99.78	$99.80	$99.80
7 purchase totals =	$1,173.10		$1,275.8487	$1,275.85	$1,275.90	$1,275.90