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	$178.72	6.291%	$189.9633	$189.96	$189.95	$190.00
Purchase #2	$97.60	12.470%	$109.7707	$109.77	$109.75	$109.80
Purchase #3	$184.68	4.148%	$192.3405	$192.34	$192.35	$192.30
Purchase #4	$188.77	9.799%	$207.2676	$207.27	$207.25	$207.30
Purchase #5	$208.96	6.573%	$222.6949	$222.69	$222.70	$222.70
Purchase #6	$73.90	6.793%	$78.92	$78.92	$78.90	$78.90
Purchase #7	$249.60	5.615%	$263.615	$263.62	$263.60	$263.60
7 purchase totals =	$1,182.23		$1,264.5720	$1,264.57	$1,264.50	$1,264.60