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	$85.57	13.267%	$96.9226	$96.92	$96.90	$96.90
Purchase #2	$75.66	9.244%	$82.654	$82.65	$82.65	$82.70
Purchase #3	$60.46	11.748%	$67.5628	$67.56	$67.55	$67.60
Purchase #4	$179.74	9.582%	$196.9627	$196.96	$196.95	$197.00
Purchase #5	$94.97	5.337%	$100.0385	$100.04	$100.05	$100.00
Purchase #6	$12.43	9.473%	$13.6075	$13.61	$13.60	$13.60
Purchase #7	$55.60	13.715%	$63.2255	$63.23	$63.25	$63.20
7 purchase totals =	$564.43		$620.9736	$620.97	$620.95	$621.00