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	$176.30	6.109%	$187.0702	$187.07	$187.05	$187.10
Purchase #2	$117.61	9.167%	$128.3913	$128.39	$128.40	$128.40
Purchase #3	$226.57	12.783%	$255.5324	$255.53	$255.55	$255.50
Purchase #4	$67.36	9.633%	$73.8488	$73.85	$73.85	$73.80
Purchase #5	$212.47	5.661%	$224.4979	$224.50	$224.50	$224.50
Purchase #6	$87.73	13.867%	$99.8955	$99.90	$99.90	$99.90
Purchase #7	$45.60	3.160%	$47.041	$47.04	$47.05	$47.00
7 purchase totals =	$933.64		$1,016.2771	$1,016.28	$1,016.30	$1,016.20