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	$130.31	7.292%	$139.8122	$139.81	$139.80	$139.80
Purchase #2	$75.83	12.215%	$85.0926	$85.09	$85.10	$85.10
Purchase #3	$240.59	4.662%	$251.8063	$251.81	$251.80	$251.80
Purchase #4	$245.72	7.250%	$263.5347	$263.53	$263.55	$263.50
Purchase #5	$80.63	9.437%	$88.2391	$88.24	$88.25	$88.20
Purchase #6	$196.77	9.712%	$215.8803	$215.88	$215.90	$215.90
Purchase #7	$97.90	11.418%	$109.0782	$109.08	$109.10	$109.10
7 purchase totals =	$1,067.75		$1,153.4434	$1,153.44	$1,153.50	$1,153.40