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	$117.27	9.384%	$128.2746	$128.27	$128.25	$128.30
Purchase #2	$166.80	11.427%	$185.8602	$185.86	$185.85	$185.90
Purchase #3	$164.58	10.168%	$181.3145	$181.31	$181.30	$181.30
Purchase #4	$40.73	7.254%	$43.6846	$43.68	$43.70	$43.70
Purchase #5	$19.55	9.130%	$21.3349	$21.33	$21.35	$21.30
Purchase #6	$187.97	8.864%	$204.6317	$204.63	$204.65	$204.60
Purchase #7	$225.96	5.506%	$238.4014	$238.40	$238.40	$238.40
7 purchase totals =	$922.86		$1,003.5019	$1,003.48	$1,003.50	$1,003.50