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	$224.46	10.796%	$248.6927	$248.69	$248.70	$248.70
Purchase #2	$139.27	13.535%	$158.1202	$158.12	$158.10	$158.10
Purchase #3	$129.41	7.681%	$139.35	$139.35	$139.35	$139.40
Purchase #4	$82.37	9.776%	$90.4225	$90.42	$90.40	$90.40
Purchase #5	$150.85	3.708%	$156.4435	$156.44	$156.45	$156.40
Purchase #6	$242.28	9.140%	$264.4244	$264.42	$264.40	$264.40
Purchase #7	$55.80	12.270%	$62.6467	$62.65	$62.65	$62.60
7 purchase totals =	$1,024.44		$1,120.1000	$1,120.09	$1,120.05	$1,120.00