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	$183.69	9.336%	$200.8393	$200.84	$200.85	$200.80
Purchase #2	$119.54	13.869%	$136.119	$136.12	$136.10	$136.10
Purchase #3	$227.58	6.454%	$242.268	$242.27	$242.25	$242.30
Purchase #4	$202.89	11.753%	$226.7357	$226.74	$226.75	$226.70
Purchase #5	$59.99	4.114%	$62.458	$62.46	$62.45	$62.50
Purchase #6	$83.94	6.365%	$89.2828	$89.28	$89.30	$89.30
Purchase #7	$56.83	10.126%	$62.5846	$62.58	$62.60	$62.60
7 purchase totals =	$934.46		$1,020.2874	$1,020.29	$1,020.30	$1,020.30