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	$102.59	3.302%	$105.9775	$105.98	$106.00	$106.00
Purchase #2	$164.75	5.340%	$173.5477	$173.55	$173.55	$173.50
Purchase #3	$110.34	5.273%	$116.1582	$116.16	$116.15	$116.20
Purchase #4	$25.54	5.709%	$26.9981	$27.00	$27.00	$27.00
Purchase #5	$142.35	3.338%	$147.1016	$147.10	$147.10	$147.10
Purchase #6	$102.96	6.475%	$109.6267	$109.63	$109.65	$109.60
Purchase #7	$191.90	7.422%	$206.1428	$206.14	$206.15	$206.10
7 purchase totals =	$840.43		$885.5526	$885.56	$885.60	$885.50