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	$158.46	5.681%	$167.4621	$167.46	$167.45	$167.50
Purchase #2	$62.96	6.861%	$67.2797	$67.28	$67.30	$67.30
Purchase #3	$125.72	4.823%	$131.7835	$131.78	$131.80	$131.80
Purchase #4	$188.55	13.432%	$213.876	$213.88	$213.90	$213.90
Purchase #5	$224.90	3.822%	$233.4957	$233.50	$233.50	$233.50
Purchase #6	$234.72	6.684%	$250.4087	$250.41	$250.40	$250.40
Purchase #7	$64.60	13.672%	$73.4321	$73.43	$73.45	$73.40
7 purchase totals =	$1,059.91		$1,137.7378	$1,137.74	$1,137.80	$1,137.80