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	$185.27	4.574%	$193.7442	$193.74	$193.75	$193.70
Purchase #2	$83.93	9.443%	$91.8555	$91.86	$91.85	$91.90
Purchase #3	$91.31	10.430%	$100.8336	$100.83	$100.85	$100.80
Purchase #4	$101.84	5.347%	$107.2854	$107.29	$107.30	$107.30
Purchase #5	$34.95	9.200%	$38.1654	$38.17	$38.15	$38.20
Purchase #6	$248.57	10.786%	$275.3808	$275.38	$275.40	$275.40
Purchase #7	$201.82	10.229%	$222.4642	$222.46	$222.45	$222.50
7 purchase totals =	$947.69		$1,029.7291	$1,029.73	$1,029.75	$1,029.80