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	$59.94	4.441%	$62.6019	$62.60	$62.60	$62.60
Purchase #2	$206.92	12.690%	$233.1781	$233.18	$233.20	$233.20
Purchase #3	$44.85	6.719%	$47.8635	$47.86	$47.85	$47.90
Purchase #4	$157.58	5.555%	$166.3336	$166.33	$166.35	$166.30
Purchase #5	$168.55	9.486%	$184.5387	$184.54	$184.55	$184.50
Purchase #6	$78.52	6.153%	$83.3513	$83.35	$83.35	$83.40
Purchase #7	$6.36	11.709%	$7.1047	$7.10	$7.10	$7.10
7 purchase totals =	$722.72		$784.9718	$784.96	$785.00	$785.00