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	$98.56	11.439%	$109.8343	$109.83	$109.85	$109.80
Purchase #2	$98.75	8.823%	$107.4627	$107.46	$107.45	$107.50
Purchase #3	$20.37	7.152%	$21.8269	$21.83	$21.85	$21.80
Purchase #4	$99.82	8.782%	$108.5862	$108.59	$108.60	$108.60
Purchase #5	$199.56	6.102%	$211.7372	$211.74	$211.75	$211.70
Purchase #6	$227.45	10.106%	$250.4361	$250.44	$250.45	$250.40
Purchase #7	$205.37	11.133%	$228.2338	$228.23	$228.25	$228.20
7 purchase totals =	$949.88		$1,038.1172	$1,038.12	$1,038.20	$1,038.00