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	$131.92	3.809%	$136.9448	$136.94	$136.95	$136.90
Purchase #2	$99.27	11.385%	$110.5719	$110.57	$110.55	$110.60
Purchase #3	$82.47	3.294%	$85.1866	$85.19	$85.20	$85.20
Purchase #4	$12.86	5.661%	$13.588	$13.59	$13.60	$13.60
Purchase #5	$179.54	9.341%	$196.3108	$196.31	$196.30	$196.30
Purchase #6	$218.72	9.855%	$240.2749	$240.27	$240.25	$240.30
Purchase #7	$38.98	11.483%	$43.4561	$43.46	$43.45	$43.50
7 purchase totals =	$763.76		$826.3331	$826.33	$826.30	$826.40