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	$146.89	6.767%	$156.83	$156.83	$156.85	$156.80
Purchase #2	$176.94	5.685%	$186.999	$187.00	$187.00	$187.00
Purchase #3	$62.27	8.526%	$67.5791	$67.58	$67.60	$67.60
Purchase #4	$236.89	13.669%	$269.2705	$269.27	$269.25	$269.30
Purchase #5	$232.88	3.156%	$240.2297	$240.23	$240.25	$240.20
Purchase #6	$114.39	7.540%	$123.015	$123.02	$123.00	$123.00
Purchase #7	$137.65	7.113%	$147.441	$147.44	$147.45	$147.40
7 purchase totals =	$1,107.91		$1,191.3643	$1,191.37	$1,191.40	$1,191.30