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	$129.32	9.790%	$141.9804	$141.98	$142.00	$142.00
Purchase #2	$230.83	13.871%	$262.8484	$262.85	$262.85	$262.80
Purchase #3	$222.87	12.414%	$250.5371	$250.54	$250.55	$250.50
Purchase #4	$17.86	13.615%	$20.2916	$20.29	$20.30	$20.30
Purchase #5	$49.79	7.458%	$53.5033	$53.50	$53.50	$53.50
Purchase #6	$156.46	6.681%	$166.9131	$166.91	$166.90	$166.90
Purchase #7	$171.32	3.835%	$177.8901	$177.89	$177.90	$177.90
7 purchase totals =	$978.45		$1,073.9640	$1,073.96	$1,074.00	$1,073.90