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	$120.48	5.742%	$127.398	$127.40	$127.40	$127.40
Purchase #2	$157.72	4.331%	$164.5509	$164.55	$164.55	$164.60
Purchase #3	$91.44	5.737%	$96.6859	$96.69	$96.70	$96.70
Purchase #4	$191.93	9.387%	$209.9465	$209.95	$209.95	$209.90
Purchase #5	$246.66	4.787%	$258.4676	$258.47	$258.45	$258.50
Purchase #6	$88.35	10.870%	$97.9536	$97.95	$97.95	$98.00
Purchase #7	$97.56	3.398%	$100.8751	$100.88	$100.90	$100.90
7 purchase totals =	$994.14		$1,055.8776	$1,055.89	$1,055.90	$1,056.00