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	$46.65	11.531%	$52.0292	$52.03	$52.05	$52.00
Purchase #2	$231.71	13.841%	$263.781	$263.78	$263.80	$263.80
Purchase #3	$157.54	9.139%	$171.9376	$171.94	$171.95	$171.90
Purchase #4	$202.86	8.396%	$219.8921	$219.89	$219.90	$219.90
Purchase #5	$146.38	6.359%	$155.6883	$155.69	$155.70	$155.70
Purchase #6	$43.34	3.310%	$44.7746	$44.77	$44.75	$44.80
Purchase #7	$134.82	9.294%	$147.3502	$147.35	$147.35	$147.40
7 purchase totals =	$963.30		$1,055.4530	$1,055.45	$1,055.50	$1,055.50