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	$168.96	10.352%	$186.4507	$186.45	$186.45	$186.50
Purchase #2	$238.79	4.182%	$248.7762	$248.78	$248.80	$248.80
Purchase #3	$164.87	4.319%	$171.9907	$171.99	$172.00	$172.00
Purchase #4	$196.55	6.464%	$209.255	$209.26	$209.25	$209.30
Purchase #5	$83.39	10.752%	$92.3561	$92.36	$92.35	$92.40
Purchase #6	$43.26	8.428%	$46.906	$46.91	$46.90	$46.90
Purchase #7	$88.71	12.846%	$100.1057	$100.11	$100.10	$100.10
7 purchase totals =	$984.53		$1,055.8404	$1,055.86	$1,055.85	$1,056.00