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	$235.25	8.340%	$254.8699	$254.87	$254.85	$254.90
Purchase #2	$88.85	8.611%	$96.5009	$96.50	$96.50	$96.50
Purchase #3	$97.31	12.475%	$109.4494	$109.45	$109.45	$109.40
Purchase #4	$90.76	11.249%	$100.9696	$100.97	$100.95	$101.00
Purchase #5	$49.44	8.762%	$53.7719	$53.77	$53.75	$53.80
Purchase #6	$244.59	10.107%	$269.3107	$269.31	$269.30	$269.30
Purchase #7	$139.64	3.341%	$144.3054	$144.31	$144.30	$144.30
7 purchase totals =	$945.84		$1,029.1778	$1,029.18	$1,029.10	$1,029.20