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	$184.89	3.195%	$190.7972	$190.80	$190.80	$190.80
Purchase #2	$126.65	8.631%	$137.5812	$137.58	$137.60	$137.60
Purchase #3	$162.33	5.753%	$171.6688	$171.67	$171.65	$171.70
Purchase #4	$235.39	8.496%	$255.3887	$255.39	$255.40	$255.40
Purchase #5	$39.73	3.747%	$41.2187	$41.22	$41.20	$41.20
Purchase #6	$39.27	11.661%	$43.8493	$43.85	$43.85	$43.80
Purchase #7	$166.40	11.688%	$185.8488	$185.85	$185.85	$185.80
7 purchase totals =	$954.66		$1,026.3527	$1,026.36	$1,026.35	$1,026.30