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	$166.81	11.175%	$185.451	$185.45	$185.45	$185.50
Purchase #2	$203.30	6.450%	$216.4129	$216.41	$216.40	$216.40
Purchase #3	$21.27	4.436%	$22.2135	$22.21	$22.20	$22.20
Purchase #4	$206.98	13.226%	$234.3552	$234.36	$234.35	$234.40
Purchase #5	$174.51	12.461%	$196.2557	$196.26	$196.25	$196.30
Purchase #6	$75.83	7.337%	$81.3936	$81.39	$81.40	$81.40
Purchase #7	$143.54	4.622%	$150.1744	$150.17	$150.15	$150.20
7 purchase totals =	$992.24		$1,086.2563	$1,086.25	$1,086.20	$1,086.40