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	$229.78	3.655%	$238.1785	$238.18	$238.20	$238.20
Purchase #2	$238.34	12.121%	$267.2292	$267.23	$267.25	$267.20
Purchase #3	$57.58	7.855%	$62.1029	$62.10	$62.10	$62.10
Purchase #4	$98.53	12.695%	$111.0384	$111.04	$111.05	$111.00
Purchase #5	$90.51	9.830%	$99.4071	$99.41	$99.40	$99.40
Purchase #6	$239.94	3.547%	$248.4507	$248.45	$248.45	$248.50
Purchase #7	$29.42	8.196%	$31.8313	$31.83	$31.85	$31.80
7 purchase totals =	$984.10		$1,058.2381	$1,058.24	$1,058.30	$1,058.20