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	$179.35	9.807%	$196.9389	$196.94	$196.95	$196.90
Purchase #2	$100.63	9.594%	$110.2844	$110.28	$110.30	$110.30
Purchase #3	$49.71	13.625%	$56.483	$56.48	$56.50	$56.50
Purchase #4	$90.46	12.572%	$101.8326	$101.83	$101.85	$101.80
Purchase #5	$210.31	6.774%	$224.5564	$224.56	$224.55	$224.60
Purchase #6	$41.53	5.589%	$43.8511	$43.85	$43.85	$43.90
Purchase #7	$219.88	11.674%	$245.5488	$245.55	$245.55	$245.50
7 purchase totals =	$891.87		$979.4952	$979.49	$979.55	$979.50